Haslett Michael R, Pink Desmond, Walters Barry, Brosnan Margaret E
Department of Biochemistry, Memorial University of Newfoundland, St. John's, NF Canada A1B 3X9.
Biochim Biophys Acta. 2004 Nov 18;1675(1-3):81-6. doi: 10.1016/j.bbagen.2004.08.008.
Delta1-pyrroline-5-carboxylate dehydrogenase (P5CDh) catalyzes the conversion of Delta1-pyrroline-5-carboxylate to glutamate in a reaction requiring NADP+ as a cofactor. Delta1-pyrroline-5-carboxylate is formed in liver from proline by proline oxidase (EC number not assigned) or from ornithine via ornithine aminotransferase. A spectrophotometric assay for P5CDh was shown to be valid if rotenone was included in the assay to prevent reoxidation of NADH. Using this new assay, liver was fractionated using differential centrifugation and the distribution of P5CDh was compared to that of appropriate marker enzymes. P5CDh is enriched only in the mitochondrial fractions, as are the mitochondrial enzymes, succinate cytochrome c reductase, proline oxidase, glutaminase, and ornithine aminotransferase. Thus, it can be concluded that P5CDh occurs only in mitochondria, not in both mitochondria and cytoplasm, as had previously been reported.
δ1-吡咯啉-5-羧酸脱氢酶（P5CDh）在需要NADP⁺作为辅因子的反应中催化δ1-吡咯啉-5-羧酸转化为谷氨酸。δ1-吡咯啉-5-羧酸在肝脏中由脯氨酸通过脯氨酸氧化酶（酶委员会编号未指定）形成，或由鸟氨酸通过鸟氨酸转氨酶形成。如果在测定中加入鱼藤酮以防止NADH再氧化，则P5CDh的分光光度测定法被证明是有效的。使用这种新方法，通过差速离心对肝脏进行分级分离，并将P5CDh的分布与适当的标记酶的分布进行比较。P5CDh仅在线粒体部分中富集，线粒体酶琥珀酸细胞色素c还原酶、脯氨酸氧化酶、谷氨酰胺酶和鸟氨酸转氨酶也是如此。因此，可以得出结论，P5CDh仅存在于线粒体中，而不是如先前报道的那样同时存在于线粒体和细胞质中。
