2Lomonosov Moscow State University, Faculty of Chemistry, Leninsky Gory 1, 119992 Moscow, Russia; fax: +7 (495) 939-0997; E-mail: email@example.com
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Received May 17, 2013; Revision received June 21, 2013
Here we report the first isolation to homogeneous forms of two glucoamylases from the fungus Penicillium verruculosum and their study in comparison with known glucoamylases from Aspergillus awamori and Aspergillus niger. Genes that encode glucoamylases from P. verruculosum were cloned and expressed in the fungus Penicillium canescens, and the recombinant glucoamylases were obtained with subsequent study of their molecular weights, isoelectric points, optimal temperature and pH values, and stability. The catalytic activities of the recombinant glucoamylases were determined in relation to soluble potato starch. Changes in molecular mass distribution and content of low molecular weight products during starch hydrolysis by glucoamylases from P. verruculosum, A. awamori, and A. niger were studied. An exo-depolymerization mechanism was established to be the pathway for destruction of starch by the glucoamylases.
KEY WORDS: starch-degrading enzymes, glucoamylase, Penicillium canescens, Penicillium verruculosum, Aspergillus niger, Aspergillus awamori