[Effect of the modification of carboxylic groups in protohemin IX on the properties of endoperoxide prostaglandin synthetase].
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.
D000818:Animals; D001051:Apoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001059:Apoproteins / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors; D006418:Heme / Q000031:analogs & derivatives*; D006427:Hemin / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D011136:Polysorbates; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D012756:Sheep; D013329:Structure-Activity Relationship
D001051:Apoenzymes; D001059:Apoproteins; D016861:Cyclooxygenase Inhibitors; D011136:Polysorbates; D006418:Heme; D006427:Hemin; D011451:Prostaglandin-Endoperoxide Synthases
Vliianie modifikatsii karboksil'nykh grupp protogemina IX na svoĭstva éndoperoksidprostaglandinsintetazy.