From there, four molecules of porphobilinogen condense together to form hydroxymethylbilane with the help of porphobilinogen deaminase.

卟胆原的四个分子一并压缩构成，羟甲基胆素在卟胆原脱氨酶的辅助下。

Then, in the cytosol, delta-aminolevulinic acid is converted to porphobilinogen, or PBG, via delta-ALA dehydratase.

随后，在细胞质中，δ-氨基乙酰丙酸转化为卟胆原，即PBG通过δ-ALA脱氢酶催化。

Note that porphobilinogen deaminase is sometimes called uroporphyrinogen I synthase or hydroxymethylbilane synthase, or HMBS for short.

卟胆原脱氨酶有时被称为尿卟啉原I合成酶或羟甲基胆素合成酶，缩略为HMBS。

This last one is caused by the excess porphobilinogen being excreted in the urine.

最后一项是由于过多卟胆原从尿液排泄。

The majority of individuals with the HMBS gene mutation and a deficiency of porphobilinogen deaminase are asymptomatic.

存在HMBS基因突变及缺乏卟胆原脱氨酶的人群大部分没有症状。

This results in the buildup of porphobilinogen and aminolevulinic acid.

这会造成大量卟胆原和氨基乙酰丙酸累积。

Now individuals with acute intermittent porphyria have a mutation of the HMBS gene which codes for the enzyme porphobilinogen deaminase.

急性间歇性卟啉病的患者存在HMBS基因的突变；该基因编码卟胆原脱氨酶。

Initially the urine is colorless, but if exposed to light the porphobilinogen oxidizes and turns a reddish, wine color.

尿液通常是无色的，但如果暴露在光照下其中的卟胆原会氧化，尿液则转变为红葡萄酒色。

The diagnosis is confirmed by measuring erythrocyte porphobilinogen deaminase activity.

可通过检测红细胞内卟胆原脱氨酶活性以确诊。

Furthermore, it causes the buildup of the earlier metabolites like porphobilinogen and aminolevulinic acid, which can be toxic to the body.

这会进一步导致大量生成早期代谢产物，比如卟胆原、氨基乙酰丙酸，对机体有害。