Mevkh A T, Golub N B, Varfolomeeva S D, Luzgina V N, Filippovich E I
Bioorg Khim. 1985 Jun;11(6):797-801.
The effect of vinyl groups of protohemin IX on its cofactor properties with respect to prostaglandin H synthetase has been studied. It was shown that substitution of ethyl groups or a hydrogen for vinyl groups affects neither binding of the prosthetic group to the apoenzyme nor catalytic properties of holo-prostaglandin H synthetase. Replacement of vinyl groups with bulkier substituents (hydroxyethyl or acetyl groups) decreases holoenzyme stability and catalytic activity. By comparison of the cofactor properties of protoporphyrin and hematoporphyrin macrocycles with different central ions (Fe3+, Mn2+, 2H+ in the case of protoporphyrin, and Fe3+, Mg2+, Cd2+ and Cu2+ in the case of hematoporphyrin), the presence of Fe3+ ions was shown to be mandatory for prostaglandin H synthetase activity. It was demonstrated that the cofactor structure modifications do not affect the holo-prostaglandin H synthetase inactivation rate constant in a reaction.
已研究了原卟啉IX的乙烯基对其作为前列腺素H合成酶辅因子性质的影响。结果表明，用乙基或氢取代乙烯基既不影响辅基与脱辅基酶的结合，也不影响全酶前列腺素H合成酶的催化性质。用体积更大的取代基（羟乙基或乙酰基）取代乙烯基会降低全酶稳定性和催化活性。通过比较不同中心离子（原卟啉中的Fe3+、Mn2+、2H+，以及血卟啉中的Fe3+、Mg2+、Cd2+和Cu2+）的原卟啉和血卟啉大环的辅因子性质，发现Fe3+离子的存在对前列腺素H合成酶活性是必需的。已证明辅因子结构修饰不会影响反应中全酶前列腺素H合成酶的失活速率常数。
