Jones C S, Mahuran D, Lowden J A, Callahan J W
Can J Biochem Cell Biol. 1984 Jun;62(6):529-34. doi: 10.1139/o84-070.
beta-Galactosidase purified to apparent homogeneity from human placenta occurred in two separable fractions. A low molecular mass form (relative mass (Mr) 170 000) is composed of a single polypeptide chain (Mr 70 000). This was derived from a larger form by molecular sieve chromatography at both low (10 mM) and high (500 mM) NaCl concentration. The larger form of beta-galactosidase also contains small amounts of two polypeptides with apparent Mr values of 23 000 and 35 000 daltons. Both forms of the enzyme hydrolyze synthetic aryl galactosides and natural glycolipid substrates at comparable rates. Antibodies raised in rabbits against the low Mr beta-galactosidase also cross-reacts with the high Mr enzyme. The antibody preparation also cross-reacted with beta-hexosaminidase even though the latter was found at very low levels in the antigen, as judged by lack of detection of representative protein bands on sodium dodecyl sulfate - polyacrylamide gel electrophoresis and enzyme activity measurements. A portion of this cross-reactivity (35%) against beta-hexosaminidase could not be absorbed from the preparation without the simultaneous loss of beta-galactosidase activity, suggesting that the two enzymes show a degree of antigenic identity.
从人胎盘中纯化至表观均一的β-半乳糖苷酶存在于两个可分离的组分中。一种低分子量形式（相对分子质量（Mr）170 000）由一条单一多肽链（Mr 70 000）组成。在低（10 mM）和高（500 mM）NaCl浓度下通过分子筛色谱法，这种低分子量形式由一种更大的形式衍生而来。β-半乳糖苷酶的更大形式还含有少量表观Mr值分别为23 000和35 000道尔顿的两种多肽。两种形式的酶以相当的速率水解合成芳基半乳糖苷和天然糖脂底物。用兔抗低Mrβ-半乳糖苷酶产生的抗体也与高Mr酶发生交叉反应。该抗体制备物也与β-己糖胺酶发生交叉反应，尽管通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳上代表性蛋白条带的检测缺失和酶活性测量判断，后者在抗原中的含量非常低。针对β-己糖胺酶的这种交叉反应的一部分（35%）在不同时丧失β-半乳糖苷酶活性的情况下无法从制备物中吸收，这表明这两种酶表现出一定程度的抗原同一性。
