Yoshinaga T, Sano S
J Biol Chem. 1980 May 25;255(10):4727-31.
Purified coproporphyrinogen oxidase catalyzed conversion of 2-beta-hydroxypropionic acid-4-propionic acid deuteroporphyrinogen IX, 2-propionic acid-4-beta-hydroxypropionic acid deuteroporphyrinogen IX, 2,4-bis (beta-hydroxypropionic acid) deuteroporphyrinogen IX, harderoporphyrinogen, and isoharderoporphyrinogen to protoporphyrinogen IX. This result suggests that the enzymatic conversion of propionate groups of coproporphyrinogen III to vinyl groups of protoporphyrinogen IX occurs stepwise starting from position 2 to 4 through beta-hydroxypropionate porphyrinogen as an intermediate. When coproporphyrinogen oxidase was treated with tetranitromethane, an initial modification of 1 tyrosine residue per molecule did not affect the enzyme activity, whereas modification of a second tyrosine residue resulted in a substantial inactivation of the enzyme. Conversion of 2,4-bis-(beta-hydroxypropionic acid) deuteroporphyrinogen XI into protoporphyrinogen IX was not affected by the tyrosine residue modification. Both modification and kinetic studies led to a conclusion that at least one tyrosine residue is involved in the active site of the enzyme, presumably participating in the initial reaction of the oxidation step of a propionate group to beta-hydroxypropionate.
纯化的粪卟啉原氧化酶催化2-β-羟基丙酸-4-丙酸氘卟啉原IX、2-丙酸-4-β-羟基丙酸氘卟啉原IX、2,4-双（β-羟基丙酸）氘卟啉原IX、硬卟啉原和异硬卟啉原转化为原卟啉原IX。该结果表明，粪卟啉原III的丙酸基团向原卟啉原IX的乙烯基的酶促转化是逐步发生的，从位置2到4以β-羟基丙酸卟啉原为中间体。当用四硝基甲烷处理粪卟啉原氧化酶时，每分子最初修饰1个酪氨酸残基并不影响酶活性，而修饰第二个酪氨酸残基会导致酶大量失活。2,4-双（β-羟基丙酸）氘卟啉原XI向原卟啉原IX的转化不受酪氨酸残基修饰的影响。修饰和动力学研究均得出结论，该酶的活性位点至少涉及一个酪氨酸残基，可能参与丙酸基团氧化为β-羟基丙酸的初始反应步骤。
