HEME SYNTHETASE DEFICIENCY IN HUMAN PROTOPORPHYRIA - DEMONSTRATION OF DEFECT IN LIVER AND CULTURED SKIN FIBROBLASTS
HEME SYNTHETASE DEFICIENCY IN HUMAN PROTOPORPHYRIA - DEMONSTRATION OF DEFECT IN LIVER AND CULTURED SKIN FIBROBLASTS
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DOI：
10.1172/jci108189
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发表时间：
1975-01-01
影响因子：
15.9
通讯作者：
MAHONEY, MJ
中科院分区：
文献类型：
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作者：
BONKOWSKY, HL;BLOOMER, JR;MAHONEY, MJ
血红素生物合成的最后一步是线粒体酶血红素合成酶催化卟啉与 Fe++ 的螯合。我们使用 59Fe 和次卟啉或原卟啉作为底物，对这种酶采用了灵敏的放射化学测定。在该方法中，铁保持亚铁状态，培养系统中排除氧气，并将标记的血红素产物提取到乙酸乙酯中。该测定已用于测量通过针活检获得的肝脏匀浆和体外培养的人皮肤成纤维细胞的超声处理中血红素合成酶的活性。此外，还测量了成纤维细胞裂解物中血红素合成途径第一种酶 δ-氨基乙酰丙酸合成酶的活性。 8 名原卟啉症患者的成纤维细胞裂解物具有 δ-氨基乙酰丙酸合成酶活性，与 8 名正常成纤维细胞系的活性没有显着差异，而以次卟啉或原卟啉为底物的血红素合成酶活性在这些患者皮肤成纤维细胞的超声处理中显着降低，平均为次卟啉对照组的 8% 和原卟啉对照组的 14%。基材。在 5 名原卟啉症患者的肝脏匀浆中，血红素合成酶活性也显着低于 6 名未患原卟啉症患者的血红素合成酶活性，平均值为原卟啉作为底物对照的 13%。这些结果证明血红素合成酶活性降低是原卟啉症血红素合成途径的基本缺陷。这种缺陷可能导致原卟啉积累，从而导致原卟啉症中观察到的生化和临床特征。
The final step in heme biosynthesis is chelation of porphyrin with Fe++ catalyzed by the mitochondrial enzyme heme synthetase. We have employed a sensitive radiochemical assay for this enzyme, using 59Fe and deuteroporphyrin or protoporphyrin as substrates. In this method iron is maintained in the ferrous state, oxygen is excluded from the incubation system, and labeled heme product is extracted into ethyl acetate. This assay has been used to measure the activity of heme synthetase in homogenates of liver, obtained by needle biopsy, and in sonicates of human skin fibroblasts, cultured in vitro. In addition, activity of the first enzyme of the heme synthetic pathway, delta-aminolevulinic acid synthetase, has been measured in fibroblast lysates. Lysates of fibroblasts from eight patients with protoporphyria had activities of delta-aminolevulinic acid synthetase which did not differ significantly from those of eight normal fibroblast lines, whereas activity of heme synthetase, with either deuteroporphyrin or protoporphyrin as substrate, was markedly decreased in sonicates of skin fibroblasts from these patients, the mean being 8% of control with deuteroporphyrin and 14% with protoporphyrin as substrate. In homogenates of liver from five patients with protoporphyria, activity of heme synthetase was also significantly less than that found in six patients without prophyria, the mean being 13% of control with protoporphyrin as substrate. These results provide evidence that decreased activity of heme synthetase is the basic defect in the heme synthetic pathway in protoporphyria. This deficiency is probably responsible for protoporphyrin accumulation and hence the biochemical and clinical features observed in protoporphyria.