CHARACTERIZATION OF THE FOLATE-DEPENDENT MITOCHONDRIAL OXIDATION OF CARBON-3 OF SERINE
CHARACTERIZATION OF THE FOLATE-DEPENDENT MITOCHONDRIAL OXIDATION OF CARBON-3 OF SERINE
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DOI：
10.1021/bi00068a027
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发表时间：
1993-05-04
期刊：
影响因子：
2.9
通讯作者：
APPLING, DR
中科院分区：
文献类型：
--
作者：
GARCIAMARTINEZ, LF;APPLING, DR
在完整的大鼠肝线粒体和超声处理的线粒体可溶性提取物中研究了丝氨酸的叶酸依赖性催化。甲酸盐和CO2都是线粒体丝氨酸碳3氧化的产物。目前的工作测试的建议[巴洛，C。K.，& Appling，D. R.（1988）Biofactors 1，171-176]，丝氨酸的碳3首先被氧化为10-甲酰基四氢叶酸，其可以被氧化为CO2或转化为甲酸盐。丝氨酸的碳3氧化为甲酸和CO2被证明是依赖于线粒体的呼吸状态。甲酸生产是最大的状态-3（积极呼吸）线粒体和最低的解偶联线粒体。与此相反，CO2的生产是最大的解偶联的线粒体和最低的抑制线粒体。甲酸生产似乎是有利的，当高浓度的NADP+和ADP存在，但没有明确的NADP+：NADPH氧化还原状态和CO2生产之间的相关性。在可溶性线粒体提取物中，CO2的产生依赖于NADP+和四氢叶酸，而甲酸的产生除了NADP+和还原叶酸辅因子外还需要ADP。然而，与CO2生产不同的是，甲酸盐生产完全依赖于叶酸辅因子的聚谷氨酰化形式。这些实验支持所提出的叶酸介导的丝氨酸氧化作为通过线粒体的一碳单元通量的主要途径。
The folate-dependent catabolism of serine was studied in intact rat liver mitochondria and soluble extracts from sonicated mitochondria. Formate and CO2 are both known to be products of the mitochondrial oxidation of carbon 3 of serine. The present work tests the proposal [Barlowe, C. K., & Appling, D. R. (1988) Biofactors 1, 171-176] that carbon 3 of serine is first oxidized to 10-formyltetrahydrofolate, which can be either oxidized to CO2 or converted to formate. Oxidation of carbon 3 of serine to formate and CO2 was shown to be dependent on the respiratory state of the mitochondria. Formate production was greatest in state-3 (actively respiring) mitochondria and lowest in uncoupled mitochondria. In contrast, CO2 production was greatest in uncoupled mitochondria and lowest in respiratory-inhibited mitochondria. Formate production appeared to be favored when high concentrations of NADP+ and ADP were present, but there was no clear correlation between the NADP+:NADPH redox state and CO2 production. In soluble mitochondrial extracts, CO2 production depended on NADP+ and tetrahydrofolate, whereas formate production required ADP in addition to NADP+ and the reduced folate cofactor. Unlike CO2 production, however, formate production showed a complete dependance on a polyglutamylated form of the folate cofactor. These experiments support the proposed folate-mediated serine oxidation as a major pathway for the flux of one-carbon units through mitochondria.