Mevkh A T, Golub N B, Varfolomeev S D, Filippovich E I, Makarov V A
Bioorg Khim. 1983 Aug;9(8):1056-62.
The effect of protohemin IX and its modified analogs (monomethyl ester, dimethyl ester, as well as monoamides with Val-Phe-OCH3 or Leu-His-OCH3) has been examined on the activity of prostaglandin endoperoxide synthetase from sheep vesicular glands (PGH-synthetase, EC 1.14.99.1, isolated as apoenzyme). For holoenzymes having the above compounds as prosthetic groups, the dissociation constants, relative activities and the apparent inactivation constants in the course of the reaction have been determined. The effect of Tween 20 on the indicated parameters for holoenzymes with protohemin IX and its mono- and dimethyl esters has been studied. Modification of one of the two carboxylic groups of protohemin IX markedly increases the dissociation constant for the respective holoenzyme and virtually does not affect catalytic activity. Modification of both carboxylic groups of protohemin IX hinder the binding with the apoenzyme and strongly reduces the catalytic activity of the holoenzyme.
已研究了原卟啉IX及其修饰类似物（单甲酯、二甲酯以及带有Val-Phe-OCH3或Leu-His-OCH3的单酰胺）对绵羊精囊前列腺素内过氧化物合成酶（PGH合成酶，EC 1.14.99.1，以脱辅基酶形式分离）活性的影响。对于以上述化合物为辅基的全酶，已测定了反应过程中的解离常数、相对活性和表观失活常数。研究了吐温20对含原卟啉IX及其单甲酯和二甲酯的全酶上述参数的影响。原卟啉IX两个羧基之一的修饰显著增加了相应全酶的解离常数，而实际上不影响催化活性。原卟啉IX两个羧基的修饰阻碍了与脱辅基酶的结合，并强烈降低了全酶的催化活性。
