Amylases higher-plant

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. 

Heavy-metal ions, such as those of mercury, silver, copper, and lead inhibit alpha-amylases in general, mercury is more effective than copper or lead. fllphfl-Amylases from higher plants are also inhibited by ammonium molybdate and L-ascorbic acid. The mechanism of inhibition is not yet known. 

Various theoretical models have been proposed to account for the distribution of products obtained on a-amylolysis. A comparison of experimental yields with those calculated for completely random hydrolysis shows that the action of higher-plant alpha-amylases cannot be explained in this way (see Table VII). The postulate that the enzymes degrade randomly to give small products (hexaose and shorter), which are resistant to further attack, does not predict yields in good agreement with experimental observation. If, however, certain bonds are assumed to be resistant to attack, whilst others are more susceptible, better agreement is obtained. For example, it has been proposed that cereal alpha-amylases do not readily attack the... 

Theoretical yields assuming a preferential attack on certain bonds have also been calculated for bean olpha-amylases, and fairly good agreement with experiment is obtained, as shown in Table VII. It is believed, therefore, that higher-plant alpha-amylases exert a random hydrolytic action on bonds removed from the ends of a D-glucosidic chain, but that bonds near the ends are attacked in a non-random manner. 

Quantitative studies have been used to confirm that the attack on amylose is not completely random. A comparison of the action patterns of alpha-amylases from higher plants and mammals shows that they are very different. At the achroic point of hydrolysis of amylose by plant enzymes, about 60% of the saccharides were larger than the... 

The hydrolytic action of beta-amylase results in the formation of maltose in the /8-anomeric form. In contrast to the widespread distribution of the a-amylolytic enzymes with their difiPering properties, the occurrence of beta-amylase appears to be restricted entirely to the higher plants and, furthermore, enzymes from different sources behave similarly. befa-Amylase appears to be a simple enzyme, and there is no evidence for the necessity of coenzymes, metals, or nonprotein active-groups. 

Very few investigations have dealt with the uptake of stable Sr " " and its possible effects on plant growth. Isermann (1981) reported, in an extended review of strontium uptake by plants and its effects on plant growth, that strontium is not primarily toxic to higher plants in the presence of calcium. Furthermore, it has some beneficial effect on cell integrity and permeability, on the net uptake of essential plant nutrients, and on respiration. Weinberg (1977) reported that for amylase, when strontium was substituted for calcium, the enzyme had full activity but varied in some physical properties. 

Higher plants Barley (endosperm) Peas, lettuce Weeds Enzyme stimulation during germination. Stimulation of amylase synthesis. Cell extension growth, especially in dwarf varieties of Pisum sativum. Effects on germination. 

Hirata, A., M. Adachi, S. Utsumi, and B. Mikami. 2004. Engineering of the pH Optimum of Bacillus Cereus Beta-Amylase Conversion of the pH Optimum from a Bacterial Type to a Higher-Plant Type. Biochemistry 43 (39) 12523-12531. 

The immediate production of maltose by jS-amylase has led to its being called maltogenic amylase. In all cases iS-amylase produces only jS-maltose and none of the a-anomers. The mechanism of the inversion of the ano-meric carbon atom during cleavage by the enzyme is unknown. The occurrences of i -amylase activity is restricted to higher plants. 

Now an example of the effectiveness of cAMP in higher plants cAMP can replace gibberellic acid in that exemplary case already alluded to (p. 204), the synthesis of a-amylase in the aleuron of barley grains. Hence it is assumed that cAMP acts as second messenger here and that its synthesis is stimulated by gibberellic acid. 

Pure-grade m. is crystallized from maltose syrups, produced by enzymatic hydrolysis of liquefied - starches or of soluble ->amyloses. M.-forming enzymes are p-> amylases from higher plants, such as barley malt, extracts from soybean or sweet potatoes or from microorganisms Pseudomonas sp. leading to hydrolyzates of mainly P-m. 

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