Brandão R L, Nicoli J R, Figueiredo A F
J Dairy Sci. 1987 Jul;70(7):1331-7. doi: 10.3168/jds.s0022-0302(87)80152-2.
Beta-D-Galactosidase was purified from a cellular extract of Fusarium oxysporum var. lini by heat shock and successive chromatography on DEAE-cellulose DE-52 and Sephadex G-100. The purified enzyme was homogeneous on SDS gel electrophoresis. It was inhibited by divalent cations such as Zn++, Mg++, and Ca++. The Michaelis constant and maximum velocity values for o-nitrophenyl beta-D-galacto-pyranoside were 6.76 mM and 816.7 mumol X mg protein-1 X min-1. The isoelectric point was 3.83, and the optimal pH and temperature were 5.0 and 55 degrees C. The estimated molecular weight of the enzyme was 224,000 by gel filtration and 36,300 by SDS-PAGE. The enzyme was considered a hexamer. o-Nitrophenyl-beta-D-galacto-pyranoside hydrolysis was activated by lactose, suggesting an allosteric nature of the enzyme.
β-D-半乳糖苷酶通过热休克以及在DEAE-纤维素DE-52和葡聚糖凝胶G-100上的连续层析，从尖孢镰刀菌亚麻专化型的细胞提取物中纯化得到。纯化后的酶在SDS凝胶电泳上呈现均一性。它受到二价阳离子如Zn++、Mg++和Ca++的抑制。对邻硝基苯基β-D-吡喃半乳糖苷而言，米氏常数和最大反应速度值分别为6.76 mM和816.7 μmol·mg蛋白-1·min-1。等电点为3.83，最适pH和温度分别为5.0和55℃。通过凝胶过滤法估算该酶的分子量为224,000，通过SDS-PAGE法估算为36,300。该酶被认为是一种六聚体。乳糖可激活邻硝基苯基-β-D-吡喃半乳糖苷的水解，这表明该酶具有别构性质。
