Two separate transhydrogenase activities are present in plant mitochondria.
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 1.6.5.3, 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.
Bykova
N V
NV
Department of Plant Physiology, Lund University, Lund, S-221 00, Sweden.
Rasmusson
A G
AG
Igamberdiev
A U
AU
Gardeström
P
P
Møller
I M
IM
D002850:Chromatography, Gel; D007425:Intracellular Membranes / Q000201:enzymology; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009250:NADP Transhydrogenases / Q000302:isolation & purification / Q000378:metabolism*; D018532:Pisum sativum / Q000201:enzymology*; D018515:Plant Leaves; D018517:Plant Roots; D011198:Solanum tuberosum / Q000201:enzymology*; D013379:Substrate Specificity
D007527:Isoenzymes; D009243:NAD; D009249:NADP; D009250:NADP Transhydrogenases