Cardiac myofibrillar creatine kinase Km is not influenced by contractile protein binding.
Subcellular microcompartmentation underlies the proposed phosphorylcreatine shuttle mechanism in mammalian cardiac tissue. In mitochondria, CK coupling to oxidative phosphorylation via adenine nucleotide translocase decreases the Km for ATP and suggests both a functional and physical integration. In the present studies, substrate Km of myofibrillar CK was unaltered when determined in the intact, native state or after removal from the myofibril. In contrast to mitochondria, close spatial proximity between cardiac myofibrillar CK and ATPase is sufficient to establish phosphorylcreatine shuttle microcompartmentation.
Dowell
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RT
Tobacco & Health Research Institute, University of Kentucky, Lexington 40546-0236.
Fu
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MC
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003402:Creatine Kinase / Q000378:metabolism*; D007527:Isoenzymes; D007700:Kinetics; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology*; D009210:Myofibrils / Q000201:enzymology*; D010085:Oxidative Phosphorylation; D051381:Rats; D013379:Substrate Specificity
D007527:Isoenzymes; D009124:Muscle Proteins; D000255:Adenosine Triphosphate; D000226:Mitochondrial ADP, ATP Translocases; D003402:Creatine Kinase