Degradation, amylase properties

In this chapter we describe the use of pea seeds to express the bacterial enzyme a-amylase. Bacterial exoenzymes like the heat stable a-amylase from Bacillus licheni-formis are important for starch hydrolysis in the food industry. The enzymatic properties of a-amylase are well understood [13,14], it is one of the most thermostable enzymes in nature and it is the most commonly used enzyme in biotechnological processes. Although fermentation in bacteria allows highly efficient enzyme production, plant-based synthesis allows in situ enzymatic activity to degrade endogenous reserve starch, as shown in experiments with non-crop plants performed under greenhouse conditions [12,15]. Finally, the quantitative and sensitive detection of a-amylase activ-... 

These hydrolytic enzymes—which take their name from the fact that the degradation products are sugars in the a-D configuration-are found in mammals, higher plants, fungi, bacteria, and Crustacea. It is now appreciated that both the properties and the detailed action pattern of an alpha-amylase depend on the source of the enzyme. 

V. Other Biochemical Properties ok the ScHABniNCER Dextrins 1. Degradation hy Amylases... 

Zhang, T. and Oates, C.G. 1999. Relationship between a-amylase degradation and physico-chemical properties of sweetpotato starches. Food Chem. 65, 157-163. 

The subcellular localization of the starch biosynthetic and degradative enzymes of spinach leaves was carried out by measuring the distribution of the enzymes in a crude chloroplast pellet and in separated components of a protoplast lysate. The enzymes which were involved in the syntheses of starch were detected in the chloroplasts, whereas some of the enzymes involved in the degradation of starch were mainly in the soluble protein fraction but were also found in the chloroplast. The digestion pattern of the amylase on amylopectin as substrate indicated that the enzyme was an a-amylase from its endo-lytic activity, but displayed properties unlike the typical a-amylase isolated from endosperm tissue. A time-sequence analysis of the starch digestion pattern in germinating... 

A large fluorescence enhancement of 2-(4-toluidinylnaphthalene)-6-sulphonate caused by amylose decreases as the substrate is degraded by amylase.This property was used to follow the enzymatic hydrolysis of amylase and to analyse the action pattern of six kinds of amylases, porcine pancreatic, Taka-amylase A, two bacterial a-amylases, soybean 3-amylase, znd Rhizopus nivewj glucoamylase (seep. 477). 

Hydroxyethylstarch (HES) is prepared from the amylopectin of waxy maize starch by hydrolysis and subsequent treatment with ethylene oxide. Amylopectin is a branched polyglucose composed of chains of a 1-4 linked glucose residues, to which a number of branches are attached by a 1-6 linkages (Aspinall 1970). When soluble amylopectin is intravenously injected into animals, it is rapidly degraded by a-amylase and is therefore unsuitable as a plasma substitute. For this reason Wiedersheim (1957) suggested substitution of amylopectin with hydroxyethyl groups to slow down the action of amylase and so extend its persistence in the circulation. He showed that such HES preparations had useful properties as plasma expanders and were relatively nontoxic. These results were subsequently confirmed and extended (Thompson et al. 1962, 1964, 1970). 

Dextrins obtained on y-irradiation of starch have been found to contain appreciable proportions of unidentified carbonyl residues. The properties of starch for starch-gel electrophoresis were improved by y-irradiation. The decreases in viscosity and iodine-absorption values, as well as the increased reducing properties, indicated that amylose and amylopectin are degraded by y-irradiation in the same way as native starches. Although each of the amylose and amylopectin components of amylomaize starch in y-irradiated and untreated samples was hydrolysed by a-amylase to the same extent, y-irradiated amylose had a low p-amylolysis limit. /-Irradiated amylomaize and com starches were hydrolysed to greater extents by a-amylase as the radiation dose was increased, and differences were detected in the products of enzymic degradation of amylomaize and corn starches following y-radiolysis. The water-soluble dextrins formed on y-irradiation of maize starch have been examined. ... 

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