Kato T, Chiu T C, Lim R, Troy S S, Turriff D E
Biochim Biophys Acta. 1979 Jul 25;579(1):216-27. doi: 10.1016/0005-2795(79)90100-4.
Glia maturation factor from the pig brain can be detected in two molecular forms: the high molecular weight form which is 200 000 dalton in size and the low molecular weight form which is 40 000 dalton in size, as determined by Sephadex gel filtration. The former accounts for 85% of the total biological activity extracted at physiologic pH. The proportion of the low molecular weight form increases following freeze-thawing and ion-exchange chromatography. In addition to the morphological effects, both forms possess mitogenic activity but no esteropeptidase activity. Both forms show similar enzyme susceptibility, being inactivated by papain, ficin and pronase but resistant to subtilisin, thermolysin and trypsin. The high molecular weight form is more resistant to denaturation by low pH, heating and urea than the low molecular weight form. The high molecular weight factor has an isoelectric point of 4.27 whereas the low molecular weight factor has one of 5.04.
通过葡聚糖凝胶过滤测定，一种是分子量为200000道尔顿的高分子量形式，另一种是分子量为40000道尔顿的低分子量形式。前者占生理pH值下提取的总生物活性的85%。冻融和离子交换色谱后，低分子量形式的比例增加。除形态学效应外，两种形式均具有促有丝分裂活性，但无酯肽酶活性。两种形式显示出相似的酶敏感性，被木瓜蛋白酶、无花果蛋白酶和链霉蛋白酶灭活，但对枯草杆菌蛋白酶、嗜热菌蛋白酶和胰蛋白酶有抗性。高分子量形式比低分子量形式更耐低pH值、加热和尿素的变性。高分子量因子的等电点为4.27，而低分子量因子的等电点为5.04。
