Next, coprophyrinogen III is brought back into the mitochondria and converted into protoporphyrinogen IX by coproporphyrinogen oxidase.

然后，粪卟啉原Ⅲ被运送回线粒体，并通过粪卟啉原氧化酶转化为原卟啉原IX。

Afterwards, hydroxymethylbilane is converted to uroporphyrinogen III and catalyzed to coproporphyrinogen III via uroporphyrinogen III cosynthase and uroporphyrinogen decarboxylase, respectively.

之后，羟甲基胆素通过尿卟啉原III协同合成酶转化为尿卟啉原III，再由尿卟啉原脱羧酶催化为粪卟啉原III。