Studies on blue copper proteins and metal complexes as electron acceptors form a reduced enzyme

用循环伏安法测定了甲基单胞菌J甲胺脱氢酶对5种蓝铜蛋白的电子转移速率。这些铜蛋白与甲胺脱氢酶的电子转移速率常数的顺序为：Alcaligenes sp.的azurin (Az-As; E_<1/2>=+270 mM(NHE)), >来自Methylobacterium extorquens AM1的amicyanin (Am-Me; +248 mV), >来自Methylomonas J的azurin-1 （Az-MJ1; +278 mV）。作为电子受体，Az-Az的活性比Az-MJ2高7.5倍，而来自甲基单胞菌AM1的伪azurin （pAz-Ac; +260 mV）几乎没有活性。这些发现不是由于蓝铜蛋白的氧化还原电位，而是由于蛋白质序列的排列。特别是蓝铜蛋白中与Cu（II）结合的乙酰咪唑基团周围的疏水性phtch似乎对与甲胺脱氢酶相互作用很重要。

The electron-transfer rates form Methylomonas J methylamine dehyrogenase to five blue copper proteins have been evaluated by cyclic voltammetry. The order of the electron-transfer rate constants from these copper proteins to methylamine dehydrogenase (E_<1/2>=ca.+100mV(NHE))) is as follows : azurin from Alcaligenes sp. (Az-As ; E_<1/2>=+270 mM(NHE)) > amicyanin from Methylobacterium extorquens AM1 (Am-Me ; +248 mV) > azurin-1 from Methylomonas J (Az-MJ1 ; +278 mV). Az-Az exhibited the higher activity bya factor of 7.5 as electron acceptors than Az-MJ2, but pseudoazurin from Methylomonas extorquens AM1 (pAz-Ac ; +260 mV) had hardly the activity. These findings are not due to the redox potentiols of blue copper proteins but the alignment of protein sequences. Espectially the hydrophobic phtch around hystidine imidazole guroup bound to Cu(II) in blue copper protein seems to be important to interact with methylamine dehydrogenase.