K. V. Avdiyuk, L. D. Vаrbanets

Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine;
e-mail: varbanets@serv.imv.kiev.ua

The current literature data on producers, physico-chemical properties and substrate specificity of α-amylases produced by microbes from different taxonomic groups such as bacteria, fungi and yeasts are discussed in the survey. Synthesis of α-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. α-Аmylases, isolated from different sources are distinguished in their physico-chemical properties, particularly in their molecular weights, рН- and thermooptimums, inhibitors and activators. The enzymes hydrolyse soluble starch, аmylose, аmylopectin, glycogen, maltodextrins, α- and β-cyclodextrins and other carbohydrate substrates. It is well known that α-amylases belong to GH-13 family of glycosyl-hydrolases, which contain the catalytic domain A as (β/α)₈-barrel. In addition to domain А, α-аmylases contain two other domains: В and С, which are localized approximately on opposite sides of (β/α)₈-barrel. Most of the known α-amylases contain calcium ion, which is located on the surface between domains А and В and plays an important role in stability and activity of the enzyme.