Isolation, Specificity, and Application of β-N-Acetylhexosaminidases from Penicillium crustosum

beta-N-acetylhexosaminidases have great potential in applied biocatalysis owing to their ability to act on a wide range of natural and modified substrates. In this work, beta-N-acetylhexosaminidases from four Penicillium crustosum strains (PcHex) were studied. The production strains showed the highest enzymatic activity in the culture medium after 11-14 days of cultivation. The specific activity of the isolated and purified PcHex of hydrolysis of 4-nitrophenyl-N-acetyl-beta-D-galactopyranoside was 15-20 U/mg protein. All isolated beta-N-acetylhexosaminidases showed similar pH-activity profiles, with the optimum pH being 4.0-5.0 and the optimum temperature being 40 degrees C-50 degrees C. Apart from standard substrates, two synthetic substrates (5-bromo-4-chloro-3-indolyl-N-acetyl-beta-D-galactoside and 2-chloro-4-nitrophenyl-beta-D-galactopyranoside) were tested and successfully hydrolyzed using beta-N-acetylhexosaminidase preparations. Maximum activity toward the fluorogenic substrate 4-methylumbelliferyl-N-acetyl-beta-D-galactopyranoside (4MU-beta-GalNAc) was observed for enzyme preparations from PcHex1 (15.38 U/mg protein) isolated from swab samples of books in the Slovak National Museum in Martin (Slovak Republic) and stored in our laboratory. The same enzyme preparation was used for the selective hydrolysis of beta-anomer of 4MU-GalNAc from an anomeric mixture of 4MU-alpha/beta-GalNAc. Thus, pure alpha-anomer (with the total yield being 90%) was separated from the mixture, which suggests the application potential of these enzymes.