Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, DF 04510, Mexico.
Biochem Biophys Res Commun. 2011 Jan 7;404(1):443-7. doi: 10.1016/j.bbrc.2010.11.141. Epub 2010 Dec 5.
Previous studies have reported that some adenosylcobalamin-dependent enzymes suffer inactivation during catalysis due to the oxidation of cobalamin. In addition, the protection or reactivation of their catalytic activities by proteins called "protectases" or reactivases is well known in bacteria. In this study, we examined the influence of human MMAA protein on the kinetics of the reaction catalyzed by methylmalonyl-CoA mutase (MCM) by testing both purified recombinant proteins in vitro. Our results showed that MMAA plays dual roles in MCM activity. When it was added at the beginning of the reaction, it prevents inactivation by guarding MCM. After 60 min of reaction, when MCM is inactive, the addition of MMAA increases the enzymatic activity through GTP hydrolysis, indicating reactivation of MCM by exchange of the damaged cofactor. Interaction between MCM and MMAA observed in vitro was confirmed in vivo by yeast two-hybrid system.
先前的研究报告指出，由于钴胺素的氧化，一些依赖腺嘌呤核苷酸钴胺素的酶在催化过程中会失活。此外，在细菌中，被称为“保护酶”或再激活酶的蛋白质对其催化活性的保护或再激活是众所周知的。在这项研究中，我们通过体外测试纯化的重组蛋白，研究了人 MMAA 蛋白对甲基丙二酰辅酶 A 变位酶（MCM）催化反应动力学的影响。我们的结果表明，MMAA 在 MCM 活性中起双重作用。当它在反应开始时添加时，它通过保护 MCM 来防止失活。反应 60 分钟后，当 MCM 失活时，添加 MMAA 通过 GTP 水解增加酶活性，表明通过交换受损辅因子使 MCM 再激活。通过酵母双杂交系统在体内证实了体外观察到的 MCM 和 MMAA 之间的相互作用。
