[Kinetic characteristics of glycosidases of Aspergillus niger 185III].

It was established, as a result of investigation of kinetic properties of two fungal glycosidases (alpha-N-acetylgalactosaminidase and alpha- galactosidase), that Km and Vmax for the corresponding synthetic substrates were 1.19 and 1.25 mM, 25.0 and 10.5 micromol/min/mg of protein, respectively. a-Galactosidase and alpha-N-acetylgalactosaminidase were also competitively inhibited by the reaction products - D-galactose and N-acetylgalactosamine, the inhibition constants were 8.5 x 10(-3) and 6.2 x 10(-2) M, respectively. One could also observe the inhibition of alpha-galactosidase reaction in the presence of 10(-3) M of fucose, lactose and arabinose. It was shown that the rate of enzymatic hydrolysis of nitrophenyl substrates was directly proportional to the concentration of enzymes, and the increase of the substrate concentration leads to the increase of hydrolysis rate. The substrate concentration being increased above the optimal one (3.6 mg/ml), the decrease of the reaction rate owing to the formation of inactive enzyme-substrate complex FS2 may be observed.