Cytosol-mitochondria transfer of reducing equivalents by a lactate shuttle in heterotrophic Euglena.

摘要: To assess the expression and physiological role of mitochondrial NAD(+)-independent lactate dehydrogenase (iLDH) in Euglena gracilis, cells were grown with different carbon sources, d- l-iLDH activities several key metabolic intermediates examined. iLDH activity was significant throughout growth period, increasing by three- to fourfold from latency stationary phase. Intracellular levels D- L-lactate high (5-40 mm) start culture increased (20-80 when phase entered. All external sources actively consumed, reaching a minimum upon entering phase, degradation paramylon started. The level ATP essentially unchanged under all experimental conditions. Oxalate, an inhibitor iLDH, strongly inhibited oligomycin-sensitive respiration growth, whereas rotenone, respiratory complex I, only slightly affected these parameters lactate-grown cells. Isolated mitochondria exhibited NADH-supported respiration, which sensitive rotenone flavone, inability oxidize pyruvate. Addition cytosol, NADH pyruvate incubated flavone prompted O2 uptake, blocked oxalate. data suggested that is independent substrate availability iLDHs play transfer reducing equivalents cytosol chain (lactate shuttle).