title: Perinatal enhancement of cardiac myofibrillar creatine kinase activity without change in enzyme Km.
abstract: Myofibrillar creatine kinase (CK) serves as one microcompartment of the phosphorylcreatine shuttle by providing ATP as substrate for adenosinetriphosphatase (ATPase). During perinatal heart development, augmentations of myofibrillar ATPase and CK occur in concert with increased contractile performance. The maximal reaction velocity (Vmax) for CK doubles during development in both intact native myofibril and enzyme extracted from myofibril. The absence of alterations in ADP and creatine phosphate substrate Michaelis constants (Km), isoenzyme composition, or total number of -SH groups suggests active site function (Vmax) is influenced indirectly via a subunit domain effect on enzyme conformation.
authors.affiliation: Tobacco and Health Research Institute, University of Kentucky, Lexington 40546-0236.
authors.forename: R T
authors.initials: RT
authors.lastname: Dowell
authors.forename: M C
authors.initials: MC
authors.lastname: Fu
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000375:Aging / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism*; D003402:Creatine Kinase / Q000378:metabolism*; D004789:Enzyme Activation; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009210:Myofibrils / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014886:Weaning
chemical_list: D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D003402:Creatine Kinase; D000251:Adenosine Triphosphatases