抄録
The purified carp blood neutral β-N-acetylglucosaminidase has been distinguished. The enzyme had a pH optimum of 6.5, but it was quite stable in pH range from 7.0 to 11.0. The enzyme was heat-labile and lost more than 90% of the activity when preincubated at 50°C for 10min. The enzyme was stimulated by dithiothreitol and 2-mercaptoethanol at a concentration of about 10mM and not inhibited by free N-acetylgalactosamine or acetate. Inhibition by divalent metal ions increased in the order of Mn2+<Zn2+<Cu2+<Hg2+, but the enzyme was activated by Co2+ and Ca2+ at a concentration of 1 mM. The Km of the enzyme for synthetic substrate, 4-methyl-umbelliferyl-2-acetamido-2-deoxy-β-D-glucopyranoside, was 0.22 mM. The neutral β-N-acetyl-glucosaminidase appeared to be specific to β-N-acetylglucosaminide derivatives. The molecular weight of the enzyme was estimated to be about 240, 000 by gel filtration and the isoelectric point (pI) was 4.2. The enzyme was stable for 6 months when kept in 50% glycerol. It is suggested that the neutral β-N-acetylglucosaminidase in carp blood may correspond to those in human, bovine and rat brain tissues.
