de Verneuil H, Grandchamp B, Nordmann Y
Biochim Biophys Acta. 1980 Jan 11;611(1):174-86. doi: 10.1016/0005-2744(80)90053-4.
Several kinetic properties of uroporphyrinogen decarboxylase (uroporphyrinogen-III carboxy-lyase, EC 4.1.1.37) from human hemoglobin-free hemolysates were studied, using substrates of both isomeric series I and III (uroporphyrinogen, hepta and pentacarboxyl porphyrinogens). Enzyme affinity for series II isomers was always found to be higher than for corresponding series I isomers. Mixed substrate experiments using porphyrinogen (both labelled with 14C and unlabelled) showed: (a) a reciprocal inhibition of decarboxylation of series III porphyrinogens by series I porphyrinogens with the same number of carboxylic groups; (b) no inhibition of hepta- and pentacarboxylic series III porphyrinogens decarboxylation by uroporphyrinogen III. It is demonstrated that porphyrinogens of both isomeric series with the same number of carboxylic groups are decarboxylated at the same active center; in contrast, the sequential decarboxylation of uroporphyrinogen III to coproporphyrinogen III occurs at four different active centers. Relationship between the kinetic properties of uroporphyrinogen decarboxylase and biological data of porphyria cutanea are discussed.
利用Ⅰ型和Ⅲ型异构体系列的底物（尿卟啉原、七羧基和五羧基卟啉原），研究了来自无血红蛋白人溶血产物的尿卟啉原脱羧酶（尿卟啉原-Ⅲ羧基裂解酶，EC 4.1.1.37）的几种动力学性质。发现该酶对Ⅱ型异构体的亲和力总是高于相应的Ⅰ型异构体。使用卟啉原（既有14C标记的，也有未标记的）进行的混合底物实验表明：（a）具有相同羧基数目的Ⅰ型卟啉原对Ⅲ型卟啉原的脱羧反应有相互抑制作用；（b）尿卟啉原Ⅲ对七羧基和五羧基系列Ⅲ型卟啉原的脱羧反应无抑制作用。结果表明，具有相同羧基数目的两种异构体系列的卟啉原在同一活性中心进行脱羧反应；相反，尿卟啉原Ⅲ依次脱羧生成粪卟啉原Ⅲ是在四个不同的活性中心进行的。本文还讨论了尿卟啉原脱羧酶的动力学性质与迟发性皮肤卟啉症生物学数据之间的关系。
