A transhydrogenase-like mechanism in CHO cells comprising concerted cytosolic reaction and mitochondrial shuttling activities.

• CIC, MPC1/2, ME cyt , and MDH cyt form transhydrogenase-like mechanism in CHO cells. • Pyruvate and malate serve as intermediary electron carriers. • Transhydrogenase-like activity provides NADPH cyt utilizing the excess NADH cyt. The proper supply and regeneration of reduction equivalents such as NADH and NADPH is of pivotal importance for living cells. Although both, NADH and NADPH, are electron carriers, they serve for different, complementing needs and require well balanced exchange. In Chinese hamster ovary (CHO) cells, the proton translocator 'Nicotinamide Nucleotide Transhydrogenase' (NNT) was annotated recently, but no in vivo operational evidence was given, yet. Here, we present another transhydrogenase-like mechanism building on the adaptive interplay of cytosolic malate dehydrogenase (MDH cyt) and cytosolic malic enzyme (ME cyt) with the mitochondrial shuttles citrate carrier (CIC), dicarboxylate carrier (DIC), and mitochondrial pyruvate carrier (MPC). The system is highly flexible using malate and pyruvate as intermediary electron carriers and quickly adapts to current needs. Indications for the existence of the mechanism are found in different monoclonal antibody producing CHO cell lines and under growing and stationary conditions. [ABSTRACT FROM AUTHOR]