Jeffery D R, Roth J A
J Neurochem. 1985 Mar;44(3):881-5. doi: 10.1111/j.1471-4159.1985.tb12898.x.
The soluble form of human brain catechol-O-methyltransferase (EC 2.1.1.6, COMT) has been purified approximately 4,000-fold from a 250,000 X g supernatant solution. The purified enzyme exhibits a molecular weight near 27,500 and a pI value equal to approximately pH 5.0. Initial velocity and product inhibition studies are consistent with an ordered reaction mechanism for soluble COMT. Tropolone, a dead-end inhibitor, exhibited a competitive pattern of inhibition when dopamine (DA) was the varied substrate and an uncompetitive pattern when S-adenosyl-L-methionine (SAM) was the varied substrate. These observations strongly suggest that the soluble form of COMT from human brain catalyzes the O-methylation of catecholamines via an ordered reaction mechanism in which SAM is the leading substrate. Since the membrane-bound form of COMT catalyzes the O-methylation of catecholamines through an identical reaction mechanism, these data provide further evidence that two forms of COMT, while being localized in distinct subcellular compartments, are quite similar in their molecular structure.
人脑儿茶酚-O-甲基转移酶（EC 2.1.1.6，COMT）的可溶性形式已从250,000×g的上清液中纯化了约4000倍。纯化后的酶分子量接近27,500，pI值约为pH 5.0。初始速度和产物抑制研究与可溶性COMT的有序反应机制一致。托酚酮是一种终产物抑制剂，当多巴胺（DA）为可变底物时表现出竞争性抑制模式，而当S-腺苷-L-甲硫氨酸（SAM）为可变底物时表现出非竞争性抑制模式。这些观察结果强烈表明，人脑COMT的可溶性形式通过一种有序反应机制催化儿茶酚胺的O-甲基化，其中SAM是主要底物。由于COMT的膜结合形式通过相同的反应机制催化儿茶酚胺的O-甲基化，这些数据进一步证明，两种形式的COMT虽然定位于不同的亚细胞区室，但其分子结构非常相似。
