Alpha Amylase Saliva Isoenzyme

Dental and Oral Biology, Biochemistry

Y. Yamakoshi , in Reference Module in Biomedical Sciences, 2014

α-Amylase

The salivary α-amylase is an endoglycohydrolase encoded by the gene Amy1. It hydrolyzes internal α-1,4-glucoside bonds of starch to the disaccharide maltose and moderate length oligosaccharides called limit dextrins. These products adhere to chewed food and hold the bolus together for swallowing.

Saliva and blood contain amylase isozyme families due to other enzymes removing variable amounts of attached glycan and amide groups from up to three asparagine residues near the C-terminus. Salivary and pancreatic amylases are also secreted into blood, where they each account for about half of the amylase content and differ from the salivary amylase family by having a greater negative charge.

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CARBOHYDRATES | Digestion, Absorption, and Metabolism

D.H. Alpers , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Salivary and Gastric Digestion

Salivary amylase is probably important in initiating starch digestion, depending upon the time spent chewing. Human salivary amylase is 94% identical with pancreatic amylase, but is inactivated in the acid pH of the gastric lumen. Starch supplements are better tolerated in breast-fed than bottle-fed infants, because of the presence of human milk amylase. In humans before 1 year of age, α-amylase activity in the duodenum is fairly low, due to delay in development of full secretory capacity. Presence of starch or its hydrolytic products can protect the enzyme from acid denaturation, and in this way some salivary or milk amylase reaches the more neutral pH of the duodenal lumen.

Gastric juice contains no other carbohydrases than α-amylase. Acid nonenzymic hydrolysis of some carbohydrates can occur, presumably in the stomach, although the extent of this process in vivo is probably small. The rate of gastric emptying is inversely related to caloric load, limiting the delivery of undigested food to the duodenum so as not to exceed hydrolytic capacity.

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Carbohydrate and Lactose Malabsorption

Richard J. Grand , ... Hans A. Büller , in Encyclopedia of Gastroenterology, 2004

Digestion

Salivary amylase initiates starch hydrolysis in the mouth, and this process accounts for not more than 30% of total starch hydrolysis. Because salivary amylase is inactivated by an acid pH, no significant hydrolysis of carbohydrates occurs in the stomach. The intraluminal intestinal phase of starch digestion depends on pancreatic amylase to complete hydrolysis, yielding oligosaccharides of varying lengths. This process is extremely rapid; 75% is completed in the proximal 2.5 feet of jejunum within 10 minutes after passage of starch into the small intestine.

The mucosal phase is characterized by surface digestion of oligosaccharides released by amylase. It also includes hydrolysis of disaccharides (maltose, sucrose, and lactose) by specific disaccharidases (maltase– glucoamylase, sucrase–isomaltase, and lactase). The rates of maltose and sucrose hydrolysis are rapid because these disaccharides are readily cleaved, and the released monosaccharides are rapidly absorbed. Lactose digestion is slower, and hydrolysis is the rate-limiting step for the overall process of absorption. The final uptake of monosaccharides is accomplished by the sodium-dependent glucose transporter (SGLT1).

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Peripheral nervous system toxicity biomarkers

T.V. Damodaran , in Biomarkers in Toxicology, 2014

Salivary amylase measurement

Most measures of salivary amylase, the enzyme that initiates the chemical breakdown in the mouth, and gastrointestinal activity, have limited use. Acinar cells, which produce salivary amylase, are innervated by sympathetic and parasympathetic pathways. Some studies have found sympathetic activity increases amylase synthesis, which increases amylase concentration in the saliva, and parasympathetic activity increases saliva flow rate with no or little effect on amylase synthesis. As these effects produce an overall increase in absolute salivary amylase output, they should be considered in relating salivary amylase to stress reactivity (Brierley-Bowers et al., 2011).

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Mucosal Secretory Immunity, Stress and*

J.A. Bosch , D. Carroll , in Encyclopedia of Stress (Second Edition), 2007

Stress and α-Amylase

Studies in the early 1980s reported that salivary α-amylase concentration increases during relaxation and decreases with acute stress. However, later studies were unable to replicate these findings and instead found that acute stress increases salivary α-amylase concentration and secretion rate. These effects are again thought to result from stress-induced sympathetic activation, which would be consistent with the findings of studies showing that α-amylase secretion is increased by administration of adrenergic agonists, electrical stimulation of the local sympathetic nerves, and physical exercise. Moreover, increases in salivary α-amylase correlate with serum norepinephrine and cardiac left ventricular ejection time, a measure of cardiac sympathetic drive. Nonetheless, recent claims that salivary α-amylase is a valid noninvasive measure of adrenergic activity should be regarded with caution. First, α-amylase is also secreted in response to nonadrenergic sympathetic transmitters, i.e., various neuropeptides. Second, α-amylase secretion is also stimulated by parasympathetic stimulation, and parasympathetic stimulation augments the effects of sympathetic stimulation.

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Sleep and Use of Green Tea With Lowered Caffeine

Keiko Unno , Yoriyuki Nakamura , in Neurological Modulation of Sleep, 2020

Effect of LCGT on sAA and Sleep

To evaluate the physiological stress response, the level of sAA was measured using a colorimetric system (Nipro Co., Osaka, Japan). 48 One unit of activity (U) per mass of enzyme is defined as the production of 1   μmol of the reduction sugar, maltose, in 1   min (NC-IUBMB, 1992). After saliva was collected using a sampling tip in the morning after waking up, sAA was measured immediately. The level of sAA in the morning was significantly lower when the elderly and middle-aged participants drank LCGT, but not when they drank SGT (Table 31.3). Since nerve excitation is commonly downregulated by the next morning, 49 the level of sAA is usually low at the time of waking up. 50,51 However, insufficient downregulation may cause higher level sAA in the morning. In other words, when sleep duration is short, sAA level becomes high in the morning. 52 Furthermore, ingestion of caffeine increases sAA level. 53

Table 31.3. Low Caffeine Green Tea (LCGT) Ingestion Lowered Salivary α-Amylase Activity (sAA) in the Morning than Standard Green Tea (SGT).

Participant sAA in the Morning
LCGT SGT
Elderly ∗113.1   ±   11.3 145.1   ±   16.9
Middle-aged ∗60.5   ±   4.3 71.7   ±   5.2

Data represent mean   ±   SEM of elderly (n   =   7) and middle-aged (n   =   19). ∗, P  <   .05.

While the levels of sAA were very different among individuals, the elderly participants with lower sAA level had longer TST and shorter total WASO, resulting in higher SE (Fig. 31.3). Although changes in sleep were almost not observed in participants of low sAA initially, the quality and length of sleep improved significantly in those patients whose sAA level decreased due to LCGT intake. 38

Figure 31.3. Correlation between salivary α-amylase activity (sAA) and each sleep parameter in elderly participants. (A) Total sleep time (TST), (B) total time spent awake during the sleep (WASO), (C) sleep efficiency (SE).

 These data are cited from Unno K, Noda S, Kawasaki Y, et al. Ingestion of green tea with lowered caffeine improves sleep quality of the elderly via suppression of stress. J Clin Biochem Nutr 2017;61:210–16.

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Chlorogenic Acid in Whole Body and Tissue-Specific Glucose Regulation

Jasmine M. Tunnicliffe , ... Jane Shearer , in Coffee in Health and Disease Prevention, 2015

86.5.1 Glucose Uptake and Absorption in the Small Intestine

Carbohydrate digestion begins in the mouth with salivary amylase breaking internal α-1,4 links of polysaccharides; this process is continued by pancreatic α-amylase in the lumen of the small intestine, producing oligo-, tri-, and disaccharides. Digestion continues at the brush border membranes, where hydrolysis of disaccharides occurs on the upper villi of enterocytes with disaccharidases cleaving the terminal α-1,4 linkages. Thus, lactase breaks down lactose; maltase cleaves maltose and maltotriose, and the sucrase–isomaltase complex splits sucrose and α-limit dextrins, respectively. This enzymatic process results in the appearance of monosaccharides: glucose, galactose, and fructose.

Glucose absorption occurs via uptake into enterocytes, mainly through sodium glucose co-transporter 1 (SGLT-1) (Figure 86.3). A sodium-potassium pump (Na+/K+-ATPase) found basolaterally on the absorptive cell drives the electrochemical gradient, with 1   mol of glucose transported with 2   mol of sodium. Intercellular glucose has three fates: some may be used for intracellular fuel; some is converted to glucose-6-phosphate, which is incorporated into vesicles where dephosphorylation occurs prior to exocytosis into blood and the remainder is directly transported into blood through the facilitated glucose transporter GLUT-2. SGLT-1 also transports galactose and the glucose analog 3-O-methylglucose, but not 2-deoxy-d-glucose (which is transported by glucose transport facilitators GLUT-1 and GLUT-2).

FIGURE 86.3. Glucose absorption attenuation by CGA.

Chlorogenic acid potentially inhibits intestinal glucose absorption by decreasing transport via sodium glucose co-transporter 1 (SGLT-1).

Numerous studies report that consumption of polyphenolic-rich foods and beverages result in a lowered postprandial plasma glucose. 23 Polyphenols, including CGA, have been shown to inhibit glucose uptake by a number of mechanisms in the intestine. Welsch et al. 24 isolated rat membrane vesicles in vitro and found glucose uptake to be reduced by 80%, 38%, and 35% with 1   mmol/l 5-CQA, ferulic acid, and caffeic acid, respectively. Other phenolic compounds have likewise been shown to reduce glucose absorption resulting in lowered glycemic index of di- and polysaccharides attributed to α-glucosidase, maltase, and α-amylase inhibition. Several possible mechanisms of action, explaining CGA induced reductions in intestinal glucose uptake have been suggested. SGLT-1 has been shown to be inhibited by several polyphenols, including epicatechin gallate and epigallocatechin gallate, two flavanols found in green tea. 25 As sodium is required for co-transportion with glucose through SGLT-1, CGA may dissipate the Na+ electrochemical gradient and limit glucose transport. Alternatively, CGA may interact with and bind to sulfhydryl groups on the SGLT-1 transporter resulting in conformational changes. Glucose transporter inhibition has also been shown by phenolic hydroxyl groups, which may play a role given that at least some CGA metabolism occurs in the small intestine.

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PEAS AND LENTILS

G. Grant , ... F. Marzo , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Trypsin/chymotrypsin Inhibitors

Peas and lentils contain Bowman–Birk-like trypsin/chymotrypsin inhibitors that inhibit the activity of these digestive enzymes in vitro and in vivo. These inhibitors are of a relatively low molecular weight (around 8–10   kDa) and are double-headed in that they inhibit two enzyme molecules simultaneously. The original Bowman–Birk inhibitors (BBI) were isolated from soyabean and were found to inhibit only trypsin and chymotrypsin in combination. However, in other legume seeds, variants capable of inhibiting two molecules of trypsin or chymotrypsin are also present. This heterogeneity in the reactivity profiles of BBI-like inhibitors makes it difficult to quantify the amounts present in the seeds or seed products. Therefore, for comparison purposes, the amount of each enzyme inhibited by a known amount of product is usually given. Alternatively, enzyme inhibitory units are calculated from the same data.

Trypsin and chymotrypsin inhibiting activity in peas and lentils varies greatly between cultivars (Table 4). Assuming that the mix of inhibitor variants leads to an average profile of one molecule trypsin and one molecule chymotrypsin inhibited per molecule inhibitor, available data suggest that peas contain 0.4–2.8   g of BBI-like inhibitor per kilogram and lentils 0.15–1.4   g   kg−1. This is comparable with the levels found in many other legumes. Soyabean has 3.2–3.7   g of BBI per kilogram. However, it also contains 4.5–9.0   g per kilogram of Kunitz trypsin inhibitors. Thus, the total trypsin inhibiting activity in soyabean is far higher than that in peas or lentils.

BBI are highly resistant to proteolysis in vitro. Nonetheless, native BBI and BBI-type inhibitors seem to be readily degraded in vivo, although 125I-BBI seems to be highly resistant to proteolysis in vivo. Native inhibitors have limited effects on digestion and absorption of dietary protein and growth of animals, even when they are included at high levels (≤10   g   kg−1) in the diet. However, BBI or BBI-like inhibitors interfere with cholecystokinin-mediated control over pancreas function and trigger hypersecretion of pancreatic trypsin, chymotrypsin and α-amylase in rats, chicks, quails, and humans. In rats, chicks, and quails, this leads to pancreas enlargement, mainly as a result of hyperplasia and hypertrophy of the acinar cells and, in the long term, may lead to tissue dysfunction and disease. The effects of the inhibitors are, however, species-specific. Thus, they induce pancreas growth in young rats, mice, hamsters, guinea-pigs, and chickens but have little or no effect on the pancreas of young pigs, cattle, monkeys, or dogs.

Pancreatic enlargement is evident in rats fed pea diets, although the increase is usually much less than observed in rats given an equivalent intake of raw soyabean. Pancreatic growth was not apparent in rats fed lentil meal, although an inhibitor-enriched fraction of lentil meal did cause enlargement.

Consumption of soyabean BBI by experimental animals appears to significantly reduce the incidence and severity of liver, colon, and mammary cancers that develop as a result of treatment with chemical carcinogens or radiation. The mechanisms by which this occurs, however, remain unclear. BBI acting through localized effects on gut endocrine cells may induce the release of a number of hormones, growth factors, or peptides that interfere with tumor cell metabolism. Alternatively, bioactive fragments of BBI absorbed from the gut may be the main protective agents. The BBI-like inhibitors of field bean have also been shown to have cancer-preventing properties. It is thus possible that pea and lentil inhibitors will have a similar protective effect. (See TRYPSIN INHIBITORS;.)

α-Amylase Inhibitors

α-Amylase inhibitors inhibit the activity of salivary and pancreatic amylase in vitro and in vivo. They can impair the growth and metabolism of animals when given at high levels in the diet but may have beneficial uses in treatment of obesity or diabetes. They are generally present in very high amounts in Phaseolus species (kidney beans, 4.3   g of inhibitor per kilogram). However, the levels in peas and lentils are very low (Table 4) and unlikely to contribute significantly to the effects of these legumes on metabolism.

Lectins

Lectins are defined as carbohydrate-binding proteins/glycoproteins other than enzymes that are present in most plant materials. They are highly resistant to proteolytic degradation in vivo and survive passage through the gastrointestinal tract. If appropriate carbohydrate receptors are present on gut epithelial cells, lectins bind to them and may be taken up systemically. As a result, lectins can potentially interfere with and modify many aspects of gut and systemic metabolism. Individual lectins vary greatly in their effects in vivo, but most species appear to be responsive to dietary lectins. (See HEMAGGLUTININS (HAEMAGGLUTININS).)

Lectins can be separated into eight general categories on the basis of their carbohydrate-binding specificity: complex, fucose, galactose, N-acetylglucosamine, mannose, mannose/glucose, mannose/maltose, and sialic acid. Some, such as soyabean agglutinin (galactose-specific), alter gut and pancreas metabolism in rats, in particular causing rapid growth of these tissues, without affecting systemic systems. A few, including kidney bean lectin (complex specificity), have additional effects on systemic hormone balance and lipid and muscle metabolism and can be very deleterious if consumed in high amounts. Others, such as pea and lentil lectins (glucose/mannose-specific) appear to have little or no effect on the body metabolism of rats.

The sensitivity of animals to lectins may, however, vary with species, age, period of exposure, gastrointestinal bacteria, diet composition, and dietary history. Thus, the glucose/mannose-specific jack bean lectin (Con A) has no effect on mature germ-free rats but has limited effects (causes small intestine and pancreas enlargement) in specific pathogen-free rats. It is, however, highly deleterious to rats carrying a salmonella infection, to suckling guinea-pigs, and to quails. The glycoconjugates expressed on the gut surface of very young animals differ greatly from those in mature counterparts; in particular, a high proportion of mannose residues are present. This is also evident in rats with a pathogen infection. In these circumstances, lectins that would not normally affect the gut may be able to bind to it and elicit changes in body metabolism.

The levels of lectins in peas and lentil are low compared with that in soyabean (Table 4) and very low by comparison with kidney bean (15–30   g   kg−1). Furthermore, in studies with mature rats, these lectins have no significant effects on metabolism. This would suggest that they are unlikely to cause problems. However, in view of the data with Con A and the number of factors that influence the sensitivity of an animal to lectin, one cannot exclude the possibility of specific circumstances where these dietary lectins have profound effects.

Young chicks do not do well when raw peas are added to their diet in low amounts but will tolerate quite high dietary inclusions if they are a few weeks old. During this period, the gut develops from its very immature form at hatching to its adult form. The gut may be susceptible to the action of pea lectin at the early stages of the maturation period.

Antigenic Proteins

Native 11S globulins (glycinin) and 7S globulins (conglycinin) of soyabean induce very adverse immune reactions in preruminant calves and newly weaned piglets, leading to gut damage, scouring, and poor performance. Pea globulins partially survive gut passage and can trigger some immune responses in preruminant calves. However, the degree to which this occurs is very much lower than that observed in soyabean-fed animals.

Lentils have been linked to allergy problems in a small number of pediatric patients. A number of possible allergens have been identified, including subunits of vicilin. The incidence of intolerance to pea proteins seems to be low.

Phytate

Phytic acid is often the main reserve of phosphorus in legumes. However, it also chelates with minerals and metals, such as calcium, magnesium, zinc, and iron, forming insoluble salts that are not readily absorbed by animals or humans. In particular, it can severely impair availability of zinc and iron. Phytate can also complex with proteins and may thereby reduce digestibility or enzyme activity.

Mineral uptake by pigs and chickens fed with soyabean-based diets is slightly impaired. Addition of phytase, a phytate-degrading enzyme, to the diet appears to counteract this effect, leading to an improvement in mineral uptake and better overall performance by the animals. However, the efficacy of this treatment can be very variable.

Phytic acid levels in peas and lentils are lower than those in kidney beans (11–17   g   kg−1) and soyabean (Table 4). None the less, they can still affect mineral metabolism, since iron absorption from a pea protein-based infant formula is significantly enhanced after enzymatic degradation of phytate.

Pea and lentil phytate can clearly have adverse effects on mineral uptake and body metabolism. However, in many cases, their impact is likely to be minimal because the mineral content of the diets is well above the requirements. Pea and lentil phytate, however, may cause significant problems if mineral intake, particularly of zinc and iron, is close to or below requirements.

Dietary phytic acid may have health-promoting properties. It can inhibit α-amylase, limit carbohydrate digestion, and lower blood glucose. There are also indications that it is hypocholesterolemic and protective against colon cancer. However, the amounts required are quite high. It is unclear whether a normal physiological intake of peas or lentils would provide sufficient phytate to have a significant health-protective effect. (See PHYTIC ACID | Nutritional Impact.)

Tannins

Tannins are present in a wide array of plant crops. Legume condensed tannins are oligomers of variously substituted flavan-3-ols, and their antinutritional effects have recently been comprehensively reviewed. These compounds can reduce enzyme activity in the gut, impair gut morphology, lower nutrient (protein, carbohydrate and lipid) digestion and absorption, reduce mineral uptake, and greatly stimulate excretion of endogenous N. Thus, at high dietary intakes, they can adversely affect animal performance.

In contrast to the antinutritional effects, dietary flavan-3-ols have also been suggested to have important roles in disease prevention, particularly of cardiovascular diseases and some forms of cancer. They may act as antioxidant and free radical scavengers, inhibit tumor initiation and promotion, and have antibacterial and angioprotective properties.

The tannin contents of peas and lentils tend to be higher than that in soyabean (Table 4). However, the levels are comparable with those in many other legume seeds. Lentils contain moderate amounts of catechins and proanthocyanidin dimers and trimers, whereas pea samples tend to have low amounts. The compounds may have health-protective effects. However, since questions still remain as to how effectively these compounds or products derived from them are absorbed from the gut and distributed throughout the body, it is difficult to assess whether a normal intake of peas or lentils will provide sufficient flavanols to have a significant beneficial effect. (See TANNINS AND POLYPHENOLS.)

Saponins

Triterpenoid saponins, found in leguminous plants, are composed of a triterpene aglycone linked to one, two, or three saccharide chains of varying size and complexity. The levels in peas and lentils are similar to, or slightly lower than, those in soyabean (Table 4) and other legume seeds. They may reduce weight gain if consumed at very high levels. However, at the levels present in peas, lentils, and soyabeans, they are considered to have no significant antinutritional effects. Saponins, however, may have beneficial effects. They have been found to be hypocholesterolemic in a number of species, owing in part to their ability to facilitate adsorption of bile acids to dietary fiber. Evidence of their efficacy in humans is not conclusive. It has also been suggested that saponins may have anticarcinogenic or antioxidant properties. (See SAPONINS.)

Fiber

Peas and lentils contain high levels of crude and total dietary fiber (Table 1). The fibers have a high binding capacity for bile acids in vitro and also promote fermentation in the hind-gut and production of butyrate in vivo. As with other dietary fibers, pea and lentil fibers are generally considered to be beneficial. However, the specific effects of these dietary fibers on metabolism remain unclear. Inclusion of pea or lentil fibers in diets appears to lower postprandial blood triglyceride levels without affecting cholesterol concentrations. However, other studies suggest that pea fibers can influence cholesterol levels in humans. Equally, studies show that pea fibers reduce or delay starch absorption and reduce the blood glucose peak, whereas others show no effect on blood glucose. This variability may be a result of differences in the test meals used or the nutritional/health status of the subjects. Pea fibers are used in the treatment of hypercholesterolemic patients. However, they are not used alone but given as part of a mixture of dietary fibers. (See DIETARY FIBER | Properties and Sources.)

Starches

Legume starches in general tend to be less digestible or more slowly digested than corn starches. This slow release means that their glycemic index is low. They can thus be useful in diets for those with impaired carbohydrate tolerance. Lentils have been found to have beneficial effects on blood glucose profiles of diabetic patients. This is due, at least in part, to the slow release property of the constituent starch combined possibly with the effects of the fiber. (See STARCH | Structure, Properties, and Determination.)

Vitamins and Minerals

Peas and lentils contain significant amounts of important vitamins and minerals. The levels of most are fairly similar in both seeds. However, lentils appear to contain higher levels of ascorbic acid, folic acid and vitamin B6 than peas but have considerably less vitamin A. (See VITAMINS | Overview.)

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Basic Aspects of Digestion and Absorption

Ghassan T. Wahbeh , Dennis L. Christie , in Pediatric Gastrointestinal and Liver Disease (Fourth Edition), 2011

Luminal Digestion

Breakdown of starch begins in the oral cavity by salivary α-amylase (mainly from the parotid gland), although limited due to the brief exposure time before swallowing. α-Amylase is inactivated by gastric acid yet some activity may be present within the food bolus. Salivary α-amylase appears in the neonatal period. Amylase is also present in breast milk and plays a more significant role in premature neonates where pancreatic amylase production is low (Figure 2-2). 5

The majority of starch digestion occurs in the duodenum through the effect of pancreatic amylase. This activity is not restricted to the lumen because amylase may adsorb to the enterocyte luminal surface. α-Amylase is an endoenzyme that cleaves the α1,4 internal links in amylose, leaving oligosaccharides: maltose (two glucose molecules) and maltriose (three glucose molecules). Because α-amylase does not cleave α1,6 bonds or their adjacent α1,4 bonds, digestion of amylopectin also leaves branched oligosaccharides (α-limit dextrins). Amylase activity produces a small amount of free glucose molecules. Only severe pancreatic insufficiency that leaves less than 10% normal amylase levels affects starch breakdown. 6

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Digestion - Absorption

Antonio Blanco , Gustavo Blanco , in Medical Biochemistry, 2017

Digestive Action of Saliva

The acinar cells produce an enzyme called ptyalin, or salivary amylase, which is involved in the digestive process initiating the hydrolysis of starch present in food. The pH for optimal activity of ptyalin is ∼7.0 and it requires the presence of Cl−.

Salivary amylase belongs to the group of endoamylases, or α amylases, which catalyze the hydrolysis of internal α-1→4 glycosidic bonds in starch. In contrast, plant amylases are β-amylases, or exoamylases, which catalyze starch hydrolysis from the chain ends. Starch consists of a linear component, amylase, and a branched component, amylopectin. Salivary amylase can completely degrade amylose. Its hydrolysis produces maltose and eventually maltotrioses (trisaccharides of glucose), when chains with an odd number of glucose molecules are digested. During digestion, amylopectin also produces limit dextrins, which are oligosaccharides of 5–10 residues containing α-1→6 bonds, corresponding to the branching points of amylopectin. Amylase is unable to act on these molecules because it only catalyzes the hydrolysis of α-1→4 bonds.

Under normal conditions, salivary amylase cannot produce complete degradation of starch molecules due to the rapid oral transit. Ptyalin continues functioning in the stomach, although briefly, since the gastric juice, which has a very low pH (about 1.5), completely inactivates it. This is why the role of ptyalin in starch digestion is limited.

Salivary ptyalin is similar to pancreatic amylase. Both are isozymes of amylase, controlled by different genes and presenting highly homologous sequences. Ptyalin absence does not lead to digestive alterations due to compensation by pancreatic amylase, which degrades the starch arriving at the second portion of duodenum.

Another digestive enzyme, salivary lipase, is secreted by the lingual Ebner glands. Lipase catalyzes the hydrolysis of ester bonds, at the sn–3 position of triacylglycerols, with short or medium sized fatty acids the hydrolysis produces 1,2-diacylglycerol and a free fatty acid;. After swallowing, it can exert some action in the stomach because it remains stable at low pH. While it plays an important digestive role in various species, its action in adult humans is not significant; it may have some relevance in infants.

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