Laury-Kleintop L D, Damjanov I, Alhadeff J A
Biochem J. 1985 Aug 15;230(1):75-82. doi: 10.1042/bj2300075.
Mouse tissues contain unusual basic isoelectric forms of alpha-L-fucosidase (with approximate isoelectric points of 8.3 and 9.0) in addition to the usual acidic and neutral forms previously described in tissues of other species. These unusual forms are very prominent in placenta and foetal tissues and comprise approx, 50-80% of total activity up to 11 days of postnatal development. By 15 days of postnatal development, the basic forms are diminished in amount and comprise not more than 25% of total activity. Neuraminidase treatment of adult mouse liver alpha-L-fucosidase led to significantly decreased amounts of acidic forms and increased amounts of the basic forms, suggesting that these forms are chemically related at least in part by sialic acid residues. Comparative kinetic studies on mouse liver, human liver and mouse placental alpha-L-fucosidases indicated that they have the same Km (0.05-0.06 mM) for 4-methylumbelliferyl alpha-L-fucopyranoside but different pH optima and thermostability properties. Mouse liver alpha-L-fucosidase has one pH optimum (5.5) and an acidic shoulder (centred around pH 4.0) compared with two distinct optima (4.3 and 6.8) for the human liver enzyme. Mouse placental alpha-L-fucosidase has a pH-activity curve comparable with that of the mouse liver enzyme except that the acidic shoulder is absent. Mouse liver alpha-L-fucosidase is considerably more thermolabile after preincubation at 50 degrees C than are the human liver and mouse placental enzymes, which gave similar thermodenaturation curves. Immunochemical studies indicated that mouse and human alpha-L-fucosidases are dissimilar antigenically but exhibit some cross-reactivity. The IgG fraction of antibody prepared in goat against human liver alpha-L-fucosidase was ineffective by itself in immunoprecipitating mouse liver alpha-L-fucosidase, but 63% and 72% of the mouse liver and placental enzymes respectively could be immunoprecipitated in the double-antibody experiments under conditions that immunoprecipitated 92% of the human liver enzyme.
除了先前在其他物种组织中描述的常见酸性和中性形式外，小鼠组织中还含有不寻常的碱性等电形式的α-L-岩藻糖苷酶（等电点约为8.3和9.0）。这些不寻常的形式在胎盘和胎儿组织中非常突出，在出生后发育至11天时，占总活性的约50-80%。到出生后15天时，碱性形式的数量减少，占总活性的比例不超过25%。用神经氨酸酶处理成年小鼠肝脏α-L-岩藻糖苷酶，导致酸性形式的数量显著减少，碱性形式的数量增加，这表明这些形式至少部分在化学上与唾液酸残基有关。对小鼠肝脏、人肝脏和小鼠胎盘α-L-岩藻糖苷酶的比较动力学研究表明，它们对4-甲基伞形酮基α-L-岩藻吡喃糖苷具有相同的Km（0.05-0.06 mM），但具有不同的最适pH值和热稳定性特性。小鼠肝脏α-L-岩藻糖苷酶有一个最适pH值（5.5）和一个酸性肩峰（以pH 4.0为中心），而人肝脏酶有两个不同的最适pH值（4.3和6.8）。小鼠胎盘α-L-岩藻糖苷酶的pH-活性曲线与小鼠肝脏酶的相似，只是没有酸性肩峰。在50℃预孵育后，小鼠肝脏α-L-岩藻糖苷酶比人肝脏和小鼠胎盘酶对热更不稳定，后两者呈现相似的热变性曲线。免疫化学研究表明，小鼠和人α-L-岩藻糖苷酶在抗原性上不同，但表现出一些交叉反应性。用山羊制备的抗人肝脏α-L-岩藻糖苷酶抗体的IgG部分本身在免疫沉淀小鼠肝脏α-L-岩藻糖苷酶时无效，但在能免疫沉淀92%人肝脏酶的条件下，在双抗体实验中，分别有63%和72%的小鼠肝脏和胎盘酶可以被免疫沉淀。
