Multiple forms of a highly purified -N-acetylhexosaminidase from hen oviduct

A β-N-acetylhexosaminidase was purified from hen oviduct to near homogeneity. At least two forms of this enzyme, a major (I) and a minor (II), were shown to exist by polyacrylamide gel electrophoresis and isoelectric focusing. Their molecular weights, as determined by gel electrophoresis, were approximately 118,000 and 158,000. On isoelectric focusing, two peaks of activity were obtained, one at pH 6.45, the other at 6.86. β-N-acetylglucosaminidase could not be separated from β-N-acetylgalactosaminidase activity by any of the procedures employed. Of a number of compounds tested as substrates, there was no difference in the ratio of hydrolysis rates of N-acetylhexosaminidase I–II, except with tri-N-acetylchitotriose and tetra-N-acetylchitotetrose.At a concentration of 6 μm Hg⁺⁺, the enzyme was completely and selectively inhibited. The inhibition was reversed entirely by thiols. Of about 20 other cations tested, only Ag⁺ inhibited the enzyme, but amounts 200 times greater were required to effect the same degree of inhibition as Hg⁺⁺.