Enzymes salivary

Suppose we start with a starch-rich meal, say one containing a lot of pasta or bread. The digestion of starches begins in the mouth. Saliva contains an enzyme, salivary amylase (aka ptyalin), which catalyzes the conversion of starch to simple sugars such as glucose. This process is completed in the small intestine under the influence of other enzymes in the amylase class. This completes the first phase of carbohydrate catabolism the conversion of complex, polymeric carbohydrates (e.g., starches) to their simple monomeric units, the sugars. 

Other sources exist for the amylases that catalyze the conversion of starch to glucose. The Peruvian campasinos (peasants) make a drink called chicha from masticated wheat, which is dried in small cakes. When water, yeast, and more ground wheat are added, the resulting mixture ferments to a beerlike beverage. The enzyme salivary amylase is the catalyst for this starch-to-glucose conversion. 

ChemLab The following table contains data obtained by measuring the activity of the enzyme salivary amylase in solutions buffered at different pH levels. 

The shift to a larger portion of carbohydrates in early humans required genetic adaptations to produce the enzyme salivary amylase. This enzyme begins the process of converting starches to sugar in the digestive system. 

Diastase or amylase is formed when malt is produced by the germination of barley grains. Malt is therefore a good source of the enzyme. Diastase is also secreted by the salivary glands (when it is known as ptyalin), and also by the pancreas. Its function is to hydrolysef starch to a mixture of maltose and dextrin ... 

Figure 36-4. Illustration of the tight correlation between the presence of RNA polymerase II and RNA synthesis. A number of genes are activated when Chirono-mus tentans larvae are subjected to heat shock (39 °C for 30 minutes). A Distribution of RNA polymerase II (also called type B) in isolated chromosome IV from the salivary gland (at arrows). The enzyme was detected by immunofluorescence using an antibody directed against the polymerase. The 5C and BR3 are specific bands of chromosome IV, and the arrows indicate puffs. B Autoradiogram of a chromosome IV that was incubated in H-uridine to label the RNA. Note the correspondence of the immunofluorescence and presence of the radioactive RNA (black dots). Bar = 7 pm. (Reproduced, with permission, from Sass H RNA polymerase B in polytene chromosomes. Cell 1982 28 274. Copyright 1982 by the Massachusetts Institute of Technology.)...

Liheratore GT, Samson A, Bladin C, Schleuning WD, Medcalf RL. Vampire bat salivary plasminogen activator (desmoteplase) A unique fibrinolytic enzyme that does not promote neurodegeneration. Stroke. 2003 34 537-543. 

Diabetic patients have reduced antioxidant defences and suffer from an increased risk of free radical-mediated diseases such as coronary heart disease. EC has a pronounced insulin-like effect on erythrocyte membrane-bound acetylcholinesterase in type II diabetic patients (Rizvi and Zaid, 2001). Tea polyphenols were shown to possess anti-diabetic activity and to be effective both in the prevention and treatment of diabetes (Choi et al, 1998 Yang et al, 1999). The main mechanism by which tea polyphenols appear to lower serum glucose levels is via the inhibition of the activity of the starch digesting enzyme, amylase. Tea inhibits both salivary and intestinal amylase, so that starch is broken down more slowly and the rise in serum glucose is thus reduced. In addition, tea may affect the intestinal absorption of glucose. 

Salivary glands Decrease resting secretory rate Increase viscosity of saliva Decrease enzyme activity of saliva... 

In humans, the structural gene locus is on chromosome 19 (M17), and the gene spans over 40 kilobases (kb) including 18 exons and 17 introns (W2, X2). Neu-roleukin, a protein that acts as both a neurotrophic factor and a lymphokine, has been isolated from mouse salivary glands (G7), and subsequently the primary structure of neuroleukin was found to be identical to that of GPI by comparison of the cDNA sequences (C7, FI). The cDNA sequence encodes 558 amino acid residues. The enzyme consists of two identical subunits with a molecular weight of approximately 63,000 and neuroleukin is active as a monomer. 

Saliva begins the process of chemical digestion with salivary amylase. This enzyme splits starch molecules into fragments. Specifically, polysaccharides, or starches, are broken down into maltose, a disaccharide consisting of two glucose molecules. Salivary amylase may account for up to 75% of starch digestion before it is denatured by gastric acid in the stomach. 

Enteric bacterial pathogens must maneuver through a lengthy stretch of hazardous terrain before they reach their intended target or infection site within a host. Initially, they must tolerate salivary enzymes having various hydrolytic activities in the mouth, followed by exposure to shedded epithelial cells in the esophagus that may prevent local bacterial adherence (Pearson and Brownlee, 2005). In the stomach, bacteria must endure another severe environment created by the secretion of digestive enzymes and hydrochloric acid (up to 0.1 M concentration and a pH as low as 1.0). Once bacteria reach the intestines, they then encoimter mechanical. 

Sulfation has also been documented in salivary proteins, specifically statherin. The enzymes in saliva are the first wave of the human digestion process and statherin prevents the precipitation of calcium phosphate in the salivary gland and saliva. Since TPST is secreted along with statherin, sulfation plays a role in digestion by binding hydroxylapatite and preventing its precipitation. 

Saliva. The salivary glands produce a slightly alkaline secretion which—in addition to water and salts—contains glycoproteins (mucins) as lubricants, antibodies, and enzymes. a-Amylase attacks polysaccharides, and a lipase hydrolyzes a small proportion of the neutral fats. a-Amylase and lysozyme, a mu-rein-cleaving enzyme (see p. 40), probably serve to regulate the oral bacterial flora rather than for digestion (see p. 340). 

These zinc-dependent endopeptidases (meprin A [EC 3.4.24.18] and meprin B [EC 3.4.24.63] ) are members of the peptidase family M12A. They catalyze the hydrolysis of peptide bonds in proteins and peptide substrates. Meprin A, a membrane-bound enzyme that has been isolated from mouse and rat kidney and intestinal brush borders as well as salivary ducts, acts preferentially on carboxyl side of hydrophobic amino acyl residues. Meprin A and B are insensitive to inhibition by phosphora-midon and thiorphan. 

In general, ethanol in low to moderate amounts, is relatively benign to most body systems. A moderate amount of ethanol causes peripheral vasodilation, especially of cutaneous vessels, and stimulates the secretion of salivary and gastric fluids the latter action may aid digestion. On the other hand, ethanol consumption in high concentrations, as found in undiluted spirits, can induce hemorrhagic lesions in the duodenum, inhibit intestinal brush border enzymes, inhibit the uptake of amino acids, and limit the absorption of vitamins and minerals. In addition, ethanol can reduce blood testosterone levels, resulting in sexual dysfunction. 

Mechanism of Action A cholinergic drug that prevents destruction of acetylcholine by inhibiting the enzyme acetylcholinesterase, thus enhancing impulse transmission across the myoneural junction. Therapeutic Effect Improves intestinal and skeletal muscle tone stimulates salivary and sweat gland secretions. 

Effect on secretions Atropine reduces the various body secretions e.g. sweat, salivary, bronchial and lacrimal etc. It also reduces the volume and total acidity of gastric secretion and, reduce the secretion of mucin and enzymes in the gastric secretions induced by cholinergic drugs. 

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