非洲爪蟾两种孵化酶分子对卵黄膜作用机制的探讨

MECHANISM OF TWO HATCHING ENZYME MOLECULES ON VITELLINE ENVELOPE DURING THE HATCHING PROCESS OF XENOPUS LAEVIS

在分离纯化非洲爪蟾孵化酶时 ,得到了 60kD和 40kD两种分子 ,用孵化酶的特异性抗GST UVS .2抗体进行Western杂交的结果证明二者均为孵化酶分子。 60kD分子很不稳定 ,在纯化过程中极易降解 ,40kD分子可能是由 60kD分子经过降解或自身降解丢失了两个CUB重复区而形成的 ,而CUB重复区很可能在对受精膜分子结构的修饰或改造中具有重要作用。在进一步验证其蛋白酶活性和生物活性时 ,发现二者几乎具有完全相同的蛋白酶活性 ,而且均具有很强的卵黄膜溶解活性。这种卵黄膜溶解活性的结果暗示了它们对早期胚胎孵化进行调节的一个可能机制 ,即二者在降解受精膜和凝胶层的不同阶段相互配合、又各自扮演了不同的角色。由此可见 ,60kD分子降解或自身降解为 40kD分子很可能是一种自然行为 ,而并非由于实验操作所致。

Two molecular forms of Xenopus hatching enzyme, 60kD and 40kD molecules, was obtained during preparation and purification. Both of them were verified as the hatching enzyme molecules, using anti GST UVS.2 antibody as the probe. 60kD molecule was digested or autodigested easily into 40kD molecule during purification. It was indicated that 40kD molecule was probably derived from 60kD molecule with its two CUB repeats lost, and the two CUB repeats may play an important role in recognizing and/or modifying of the molecular structure of vitelline envelope. When the proteolytic and VE solubilizing activities of 60kD and 40kD molecules were further verified, it was found that both of them had very high proteolytic and also VE solubilizing activities. Almost the same VE solubilizing activity of both of them may present us a possible mechanism in the solubilization of vitelline envelope in early embryos. Therefore, it can be concluded that 1) 60kD and 40kD molecules may co ordinates with each other in the solubilization of vitelline envelope and the inner jelly layer, and each plays a different role in the different time of hatching process; 2) the digestion or autodigestion of 60kD molecules into 40kD molecules is probably a natural behavior, not just resulted from manipulations.