Metabolism of vitamin B-6 by human liver.
Metabolism of vitamin B-6 by human liver.
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DOI：
10.1093/jn/114.9.1664
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发表时间：
1984-09
期刊：
影响因子：
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通讯作者：
Alfred H. Merrill;J. Henderson;Elaine Wang;Bill W. McDonald;W. Millikan
中科院分区：
文献类型：
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作者：
Alfred H. Merrill;J. Henderson;Elaine Wang;Bill W. McDonald;W. Millikan
采用针对小样本优化的方法，分析了5例无肝病患者肝活检样本中代谢维生素B-6的酶。吡哆醛激酶（EC 2.7.1.35）活性为每克组织11.2 +/- 3.6 nmol/min，每毫克可溶性蛋白0.16 +/- 0.05 nmol/min（平均值+/- SD）；观察到锌作为二价阳离子的活性明显依赖。当以N-（5'-磷酸吡哆醇基）[3H]色胺为底物时，吡哆醇（Pyridoxine） 5'-磷酸氧化酶（EC 1.4.3.5）的活性为每毫克蛋白质0.64 +/- 0.22 pmol/分钟，每克组织47 +/- 19 pmol/分钟。当核黄素5′-磷酸被忽略时，活性降低了63 +/- 18%；因此，看起来氧化酶只是部分饱和了它的辅助因子。在碱性条件下，吡哆醛5′-磷酸水解酶活性为282 +/- 183 nmol/min / g组织，4.0 +/- 3.2 nmol/min / mg颗粒蛋白。吡哆醛被可溶性酶迅速氧化为吡哆酸（每克组织28.1 +/- 19.8 nmol/min，每毫克可溶性蛋白0.37 +/- 0.24 nmol/min），其速率不受吡啶核苷酸的影响。这些实验首次对人体肝脏中负责代谢维生素B-6的酶进行了定量分析，为解释人体利用维生素B-6的药代动力学提供了数据，并为研究这种营养物质代谢异常的疾病提供了方法。
The enzymes that metabolize vitamin B-6 were analyzed in liver biopsy samples from five patients without hepatic disease by using methods optimized for small samples. Pyridoxal kinase (EC 2.7.1.35) activities were 11.2 +/- 3.6 nmol/minute per gram of tissue and 0.16 +/- 0.05 nmol/minute per milligram of soluble protein (mean +/- SD); a clear dependence of the activity on zinc as the divalent cation was observed. Pyridoxine (pyridoxamine) 5'-phosphate oxidase (EC 1.4.3.5) activities, when using N-(5'-phosphopyridoxyl)-[3H]tryptamine as the substrate, were 0.64 +/- 0.22 pmol/minute per milligram of protein and 47 +/- 19 pmol/minute per gram of tissue. The activities were 63 +/- 18% lower when riboflavin 5'-phosphate was omitted from the assay; hence, it appears the oxidase is only partially saturated with its cofactor. The pyridoxal 5'-phosphate hydrolase(s) activities at alkaline pH were 282 +/- 183 nmol/minute per gram of tissue and 4.0 +/- 3.2 nmol/minute per milligram of particulate protein. Pyridoxal was rapidly oxidized to pyridoxic acid (28.1 +/- 19.8 nmol/minute per gram of tissue and 0.37 +/- 0.24 nmol/minute per milligram of soluble protein) by soluble enzyme(s), and the rate was unaffected by pyridine nucleotides. These experiments constitute the first quantitative analyses of the enzymes responsible for metabolizing vitamin B-6 in human liver, and provide data for interpreting the pharmacokinetics of B-6 utilization by humans, as well as methods for investigating diseases with aberrant metabolism of this nutrient.