Two separate transhydrogenase activities are present in plant mitochondria
- Molecular Cell Biology
Inside-out submitochondrial particles from both potato tubers and pea leaves catalyze the transfer of hydride equivalents from NADPH to NAD+ as monitored with a substrate-regenerating system. The NAD+ analogue acetylpyridine adenine dinucleotide is also reduced by NADPH and incomplete inhibition by the complex I inhibitor diphenyleneiodonium (DPI) indicates that two enzymes are involved in this reaction. Gel-filtration chromatography of solubilized mitochondrial membrane complexes confirms that the DPI-sensitive TH activity is due to NADH-ubiquinone oxidoreductase (EC 126.96.36.199, complex I), whereas the DPI-insensitive activity is due to a separate enzyme eluting around 220 kDa. The DPI-insensitive TH activity is specific for the 4B proton on NADH, whereas there is no indication of a 4A-specific activity characteristic of a mammalian-type energy-linked TH. The DPI-insensitive TH may be similar to the soluble type of transhydrogenase found in, e.g., Pseudomonas. The presence of non-energy-linked TH activities directly coupling the matrix NAD(H) and NADP(H) pools will have important consequences for the regulation of NADP-linked processes in plant mitochondria.
- Biochemistry and Molecular Biology
- ISSN: 0006-291X