[Microbial alpha-amylases: physicochemical properties, substrate specificity and domain structure].

The current literature data on producers, physico-chemical properties and substrate specificity of a-amylases produced by microbes from different taxonomic groups such as bacteria, fungi and yeasts are discussed in the survey. Synthesis of alpha-amylase majority is an inducible process which is stimulated in the presence of starch or products of its hydrolysis. It is possible to increase enzymes activity level by optimization of cultivation conditions of strains-producers. alpha-Amylases, isolated from different sources are distinguished in their physico-chemical properties, particularly in their molecular weights, pH- and thermooptimums, inhibitors and activators. The enzymes hydrolyse soluble starch, amylose, amylopectin, glycogen, maltodextrins, alpha- and beta3-cyclodextrins and other carbohydrate substrates. It is well known that alpha-amylases belong to GH-13 family of glycosyl-hydrolases, which contain the catalytic domain A as (beta/alpha)8-barrel. In addition to domain A, alpha-amylases contain two other domains: B and C, which are localized approximately on opposite sides of (beta/alpha)8-barrel. Most of the known alpha-amylases contain calcium ion, which is located on the surface between domains A and B and plays an important role in stability and activity of the enzyme.