A-amylase secretion

Roles of Metabolites of Abscisic Acid. Nothing is known about the physiological role of PA and DPA in plants, although these two metabolites of ABA have been tested in several bioassays recently. In the cotton explant abscission assay PA had one-tenth of the activity of ABA (19). PA and DPA were equally effective in inhibiting a-amylase secretion by barley aleurone layers treated with glbberellin A3 DPA had approximately one-tenth of the activity of ABA in this system (74). The effect of PA on growth of bean embryos was negligible (75). 

Prior to a race, many marathon runners will try to increase their glycogen concentrations by loading up with foods with a high starch content, such as pasta. a-Amylase secreted by the pancreas will digest the starch into which of the following major products ... 

Okano K, Kimura S, Narita J, Fukuda H, Kondo A. (2007). Improvement in lactic acid production from starch using a-amylase-secreting Lactococcus lactis cells adapted to maltose or starch. Appl Microbiol Biotechnol, 75, 1007-1013. 

Okano K, Zhang Q, Shinkawa S, Yoshida S, Tanaka T, Fukuda H, Kondo A. (2009c). Efficient production of optically pure D-lactic acid from raw corn starch by using genetically modified L-lactate dehydrogenase gene-deficient and a-amylase-secreting Lactobacillus plantarum strain. Appl Environ Microbiol, 75, 462-467. 

Exocellular Protein and a-amylase Secretion in Bacillus substilis J. PazlarovA... 

EXOCELLULAR PROTEIN AND a-AMYLASE SECRETION IN BACILLUS SUBTILIS... 

Figure 5.3 Direct conversion of starch to ethanol using (a) amylase-secreting or (b) amylase-displaying yeast cells.

In addition to proteases, other inhibitors reduce the activity of amylase and other digestive enzymes (Ishimoto et al, 1999). Many varieties of beans produce a glycoprotein that complexes with and inhibits a-amylase (Mirkov et al, 1995). The amylase inhibitors are non-competitive and thermostable (Gallaher and Schneeman, 1986) and, unlike protease inhibitors, do not elicit heightened secretion of amylase (Toskes, 1986). Although over-expression... 

There is evidence that protease inhibitors selectively regulate the activity of specific digestive enzymes at the level of gene expression (Rosewicz et al., 1989). Specifically, soybean trypsin inhibitor increases secretion of proteases, including a form of trypsin that is resistant to inhibition but does not cause an increase in amylase secretion. Although the relationships between protease inhibitors and exocrine pancreatic secretion have received the most attention, pancreatic secretion is increased when potato fiber is added to the diet (Jacob et al., 2000), although the mechanism and signaling pathway have not been elucidated. 

As indicated in Table 2.1, most of the promoters used in plant tissue culture have been based on the constitutive cauliflower mosaic virus (CaMV) 35S promoter. In contrast, inducible promoters have the advantage of allowing foreign proteins to be expressed at a time that is most conducive to protein accumulation and stability. Although a considerable number of inducible promoters has been developed and used in plant culture applications, e.g. [32-37], the only one to be applied thus far for the production of biopharmaceutical proteins is the rice a-amylase promoter. This promoter controls the production of an a-amylase isozyme that is one of the most abundant proteins secreted from cultured rice cells after sucrose starvation. The rice a-amylase promoter has been used for expression of hGM-CSF [10], aranti-trypsin [12, 29, 38, 39] and human lysozyme [30]. 

Enzymes that perform the same catalytic function are known as homologous enzymes and fall into two classes. Heteroenzymes are derived from different sources and although they catalyse the same reaction they show different physical and kinetic characteristics. The hydrolytic enzyme a-amylase (EC 3.2.1.1) is found in the pancreatic secretion in man and is different from the enzymes of the same name which are derived from bacteria or malt. Iso-enzymes, sometimes referred to as isozymes, are different molecular forms of the same enzyme and are found in the same animal or organism although they often show a pattern of distribution between tissues. 

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). 

Glycogen and starch ingested in the diet are hydrolyzed by a-amylases, enzymes in saliva and intestinal secretions that break (al—>4) glycosidic bonds between glucose units. Most animals cannot use cellulose as a fuel source, because they lack an enzyme to hydrolyze the (fil—>4) linkages. Termites readily digest cellulose... 

When the acidic stomach contents reach the small intestine, they are neutralized by bicarbonate secreted by the pancreas, and pan creatic a-amylase continues the process of starch digestion. 

Four major enzyme groups are secreted lipolytic, proteolytic, amylolytic, and nucleic acid splitting enzymes. These pancreatic enzymes, some of which are secreted in multipile forms, possess specificities complementary to die intestinal membrane-bound enzymes (Tabic 1). Fresh, uncontsnkinated pancreatic juice is without proteolytic activity because these enzymes am in the form of inactive zymogens. An important fraction of the calcium in pancreatic juice accompanies the enzymes, especially ct-amylase. Human pancreatic juice is moat dose to that of the pig, with high proportions of lipase and a-amylase in comparison with other mammals [1]. Therefore, pig pancreas extract, pancreatin, has up to now been die oreferred enzvme source for therapeutic tuncreas substitution. 

A large number of hyperthermophilic Archaebacteria, especially the deep sea Thermococcale and Sulfolobus species elaborate a-amylases.79-82 Many have been cloned and sequenced.78 Pyrococcus furiosus,83,84 Thermococcus profundus,85 Thermococcus hydrothermalis,78 Sulfolobus solfataricus and Sulfolobus acidocaldar-iusS6 secrete thermophilic a-amylases. The a-amylases of all of these organisms have optimal enzyme activity at 90°C or higher and often only begin to show activity at 40°C or 50°C. Pyrococcus furiosus secretes an a-amylase with an optimum temperature of 100°C and a maximum temperature of 140°C.87 The optimum pH values vary between 5 and 9. Table 7.1 summarizes the names of the organisms, the optimum temperature, and optimum pH values for several of these enzymes. 

A few chimeric enzymes have been constructed by adding one or more domains from one amylolytic enzyme to another. Some of these chimeric enzymes have been studied in regard to the secretion of the enzyme,187 substrate specificity188 and product specificity.189 A starch binding domain from a Bacillus sp. cyclomaltodextrin glucanosyltransferase was fused with B. subtilis a-amylase, and an a-amylase was... 

Ito et al. (1994) studied the inhibition of CCK-8-induced pancreatic amylase secretion by a cholecystokinin type-A receptor antagonist in rats. 

High-Level Synthesis and Secretion of a-Amylase from Rice Callus... 

This low expression in Tan-ginbozu callus, however, was not increased by exogenous gibberellic acid. Surprisingly, shoot-derived callus also secreted a-amylase at levels similar to seed-derived callus, even though shoot tissue normally produces only low levels of intracellular a-amylase. 

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