底物对变性酶的修复作用

Restoration of A Denatured Enzyme by Substrate

兎肌肌酸激酶被LDS变性后,底物能够诱导变性酶使其活力和构象得到部分恢复。变性程度不同的酶,构象和活力的恢复程度也不同:低浓度LDS变性酶,恢复程度较高;反之亦然。活力的恢复与构象的恢复两者呈对应关系。底物修复作用的pH以8.2为好。底物修复作用受其它蛋白质(例如BSA)存在的影响。等速电泳结果表明,BSA能竞争性结合LDS-酶复合物的LDS,使酶成为游离酶。变性酶先与BSA保温再加底物所得的活力恢复,大约是变性酶与含BSA的底物保温所得活力的10倍。这一结果似表明LDS变性酶仍能结合底物;被结合的底物还能使变性酶的构象发生变化。

Addition of creatine kinase denatured by lithium dodecy-lslfate (LDS) to the substrate system, both the confomation and activity of the denatured enzyme were partially restored. In this paper, some factors that may affect the restoration are reported. (1) Extent of restoration of both the conformation and activity of the denatured enzyme depends on the concentration used for denaturation. Restoration of the activity is parallel to that of the conformation. (2) The perferential pH for the restoration of activity is approximately 8.2. (3) The restoration of activity is affected by the presence of other proteins, e.g. the effect of BSA is due to the fact that it may combine with LDS bound to the creatine kinase, cause free enzyme molecules release. (4) Restored activity of denatured enzyme incubated first with only BSA then also with substrates is ten times higher than that of the denatured enzyme a incubated at once with the mixture of BSA aud substrates. This result iudicates that the substrates may bind with the denatured enzyme, and induce changes toward native or nativelike conformatiou.