ウシ乳清中のβ-Acetylglucosaminidase

抄録

Some properties of β-acetylglucosaminidase in bovine milk whey have been studied. The optimum at pH 4.4 and the Km value 1.13±0.062 (S.D.) mM were obtained for the crude enzyme in whey, using p-nitrophenyl N-acetylglucosaminide as a substrate. By carboxy methyl cellulose column chromatography of the whey protein, most of the enzyme activities appeared as a peak (a) at pH 5.0 and two peaks (b₁ and b₂) at pH 5.5. The Km values for a, b₁, and b₂ were respectively 1.19±0.077, 1.17±0.018, and 0.90±0.047 mM. Both the majority of the enzyme activities and the highest specific activity were found in "globulin and proteose-peptone fraction" obtained by the fractionation of whey protein with sodium sulfate. Heat stability of the enzyme in whey (at pH 4.4) and raw skimmed milk (at pH 6.9) was examined. The commercial milk sterilized by the ultrahigh temperature method did not show any β-acetylglucoaminidase activity.