Short-term regulation of the mammalian pyruvate dehydrogenase complex.

In this minireview the main mechanism of control of mammalian pyruvate dehydrogenase complex (PDHC) activity by phosphorylation-dephosphorylation is presented in the first place. The information recently obtained in several laboratories includes new data about isoforms of the PDH converting enzymes (kinase and phosphatase) and their action in view of short-term regulation of PDHC. Moreover, interesting influence of exogenous thiamine diphosphate (TDP) and some divalent cations, especially Mn(2+), on the kinetic parameters of PDHC saturated with endogenous tightly bound TDP, is discussed. This influence causes a shortening of the lag-phase of the catalyzed reaction and a strong decrease of the K(m) value of PDHC mainly for pyruvate. There are weighty arguments that the effects have an allosteric nature. Thus, besides reversible phosphorylation, also direct manifold increase of mammalian PDHC affinity for the substrate by cofactors seems an important aspect of its regulation.