Regulation of Pyruvate Dehydrogenase in Isolated Cardiac Myocytes and Hepatocytes by Cytosolic Calcium
It is well established that the Ca2+ ion plays a central role as a mediator of excitationcontraction and stimulus-secretion coupling (see, e.g., Katz, 1970; Rasmussen, 1981). Per haps less well known is the role that this ion also plays in activating mitochondrial oxidation and thereby making available ATP at an increased rate to match the increased energy demands associated with contraction and secretion. This activation has been most clearly established for glycerol-3-phosphate dehydrogenase (Hansford and Chappell, 1967), pyruvate dehydrogenase phosphatase (Dentonet al., 1972; Pettitet al., 1972), NAD-isocitrate dehydrogenase (Dentonet al., 1978), and 2-oxoglutarate dehydrogenase (McCormack and Denton, 1979). In the case of pyruvate dehydrogenase phosphatase, activation by micromolar concentrations of Ca2+ ions leads to the generation of an increased amount of the active, dephospho, form of the pyruvate dehydrogenase complex (PDHA) (for reviews, see Hansford, 1980; Wieland, 1983). In the case of the other three dehydrogenases, activation is of an allosteric nature, and results in a decreasedK m for the substrate.
KeywordsCardiac Myocytes Pyruvate Dehydrogenase Pyruvate Dehydrogenase Complex Transport Cycle Actomyosin ATPase
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