The human PICD gene encodes a cytoplasmic and peroxisomal NADP+-dependent isocitrate dehydrogenase
The human PICD gene encodes a cytoplasmic and peroxisomal NADP+-dependent isocitrate dehydrogenase
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DOI：
10.1074/jbc.274.43.30527
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发表时间：
1999-10-22
影响因子：
4.8
通讯作者：
Gould, SJ
中科院分区：
文献类型：
--
作者：
Geisbrecht, BV;Gould, SJ
通过同源性探测与苏氏酿酒酵母IDP3P的蛋白质序列（一种过氧化物酶体NADP（+） - 依赖性异位酸异位酸盐脱氢酶的蛋白质序列）的数据库来鉴定人PICD。人PICD cDNA包含一个1242碱基对开放式阅读框，其推导的蛋白质序列与酵母IDP3P相同59％。 PICD的表达部分挽救了酵母IDP3缺失突变体的脂肪酸生长缺陷，这表明PICD在功能上与IDP3同源。对细菌表达的PICD的动力学研究表明，该酶催化异位酸的氧化脱羧为2-氧化甲酸酯，具有22.5单位/mg的特异性活性，该PICD显示为NADP（NADP（+）112 MU m的K-M值为76 MU M值。在亚细胞分级实验中，我们发现了人和大鼠肝细胞的过氧化物酶体和细胞质中的PICD，约有与过氧化物酶体相关的总PICD蛋白的27％。 PICD在哺乳动物过氧化物酶体中的存在表明在NADPH再生中的作用，例如腹中异构异菌性减少，例如将2,4-二烯酰基-COAS转化为3-烯酰基-COAS，以及在过氧化物酶体反应中的转化，这些反应消耗了2-胶质，即苯甲酸的α-羟基化。至于细胞质PICD，葡萄糖-6-磷酸脱氢酶缺乏症患者的表型（Luzzatto，L。和Mehta，A（1995），A（1995）在遗传疾病的代谢和分子碱基（Scriver，C。R. W. S.和Valle，D。，ed。 3367-3398，McGraw-Hill Inc.，纽约）表明，PICD在细胞质NADPH产生中起重要作用，尤其是在不利于使用己糖单磷酸根分流的条件下（Luzzatto等人）。
Human PICD was identified by homology probing the data base of expressed sequence tags with the protein sequence of Saccharomyces cerevisiae Idp3p, a peroxisomal NADP(+)-dependent isocitrate dehydrogenase. The human PICD cDNA contains a 1242-base pair open reading frame, and its deduced protein sequence is 59% identical to yeast Idp3p. Expression of PICD partially rescued the fatty acid growth defect of the yeast idp3 deletion mutant suggesting that PICD is functionally homologous to Idp3p. Kinetic studies on bacterially expressed PICD demonstrated that this enzyme catalyzed the oxidative decarboxylation of isocitrate to 2-oxoglutarate with a specific activity of 22.5 units/mg and that PICD displayed K-M values of 76 mu M for isocitrate and 112 mu M for NADP(+). In subcellular fractionation experiments, we found PICD in both peroxisomes and cytoplasm of human and rat liver cells, with approximately 27% of total PICD protein associated with peroxisomes. The presence of PICD in mammalian peroxisomes suggests roles in the regeneration of NADPH for intraperoxisomal reductions, such as the conversion of 2,4-dienoyl-CoAs to 3-enoyl-CoAs, as well as in peroxisomal reactions that consume 2-oxoglutarate, namely the alpha-hydroxylation of phytanic acid. As for cytoplasmic PICD, the phenotypes of patients with glucose-6-phosphate dehydrogenase deficiency (Luzzatto, L., and Mehta, A (1995) in The Metabolic and Molecular Bases of Inherited Disease (Scriver, C. R., Beaudet, A. L., Sly, W. S., and Valle, D., eds) Vol. 3, 7th Ed., pp. 3367-3398, McGraw-Hill Inc., New York) suggest that PICD serves a significant role in cytoplasmic NADPH production, particularly under conditions that do not favor the use of the hexose monophosphate shunt (Luzzatto et al.).