Adenosine 5 -triphosphate--creatine phosphotransferase from dystrophic mouse skeletal muscle. A genetic lesion associated with the catalytic-site thiol group

Abstract

1. A column procedure for the purification of creatine kinase from normal and dystrophic mouse muscle is described. 2. The native enzymes are indistinguishable by various physical criteria and have mol.wt. about 80000. 3. The purified enzyme from dystrophic muscle is only half as active as the normal, contains only one thiol group readily alkylated by iodoacetamide instead of two and has one less free thiol group/mol. 4. Michaelis constants for MgATP and creatine are the same for both preparations. 5. The inhibitor constant for ADP at pH9.0 is different in the two enzymes and this may account for the different degrees of inhibition observed in vitro with the drug Laevadosin. 6. The enzyme from dystrophic muscle is protected by an equilibrium mixture of substrates against inhibition by iodoacetamide to a greater extent than the normal enzyme. 7. ;Fingerprinting' suggests one peptide difference between creatine kinases from normal and dystrophic muscle. 8. The possibility that this finding represents the primary lesion in dystrophy is discussed.