tailieunhanh - Báo cáo khoa học: 2-Oxo acid dehydrogenase complexes in redox regulation Role of the lipoate residues and thioredoxin

Anumber of cellular systems cooperate in redox regulation, providing metabolic responses according to changes in the oxidation (or reduction)of the redox active components of a cell. Key systems of central metabolism, such as the 2-oxo acid dehydrogenase complexes, are important participants in redox regulation, because their function is controlled by the NADH/NAD + ratio and the complex-bound dihydro-lipoate/lipoate ratio. | Eur. J. Biochem. 270 1036-1042 2003 FEBS 2003 doi MINIREVIEW 2-Oxo acid dehydrogenase complexes in redox regulation Role of the lipoate residues and thioredoxin Victoria I. Bunik Institute of Physico-Chemical Biology Moscow State University Russia A number of cellular systems cooperate in redox regulation providing metabolic responses according to changes in the oxidation or reduction of the redox active components of a cell. Key systems of central metabolism such as the 2-oxo acid dehydrogenase complexes are important participants in redox regulation because their function is controlled by the NADH NAD ratio and the complex-bound dihydro-lipoate lipoate ratio. Redox state of the complex-bound lipoate is an indicator of the availability of the reaction substrates 2-oxo acid CoA and NAD and thiol-d isuliide status of the medium. Accumulation of the dihydrolipoate intermediate causes inactivation of the first enzyme of the complexes. With the mammalian pyruvate dehydrogenase the phosphorylation system is involved in the lipoate-dependent regulation whereas mammalian 2-oxoglutarate dehydrogenase exhibits a higher sensitivity to direct regulation by the complex-bound dihydrolipoate lipoate and external SH S-S including mitochondrial thioredoxin. Thioredoxin efficiently protects the complexes from selfinactivation during catalysis at low NAD . As a result 2-oxoglutarate dehydrogenase complex may provide succi-nyl-CoA for phosphorylation of GDP and ADP under conditions of restricted NAD availability. This may be essential upon accumulation of NADH and exhaustion of the pyridine nucleotide pool. Concomitantly thioredoxin stimulates the complex-bound dihydrolipoate-dependent production of reactive oxygen species. It is suggested that this side-effect of the 2-oxo acid oxidation at low NAD in vivo would be overcome by cooperation of mitochondrial thioredoxin and the thioredoxin-dependent peroxidase SP-22. Keywords .

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