PURIFICATION AND CHARACTERIZATION OF HUMAN SARCOMERIC MITOCHONDRIAL CREATINE-KINASE

In order to set the basis for detailed clinical investigations, mitoch ondrial creatine kinase (Mi-CK) was purified to homogeneity from human cardiac muscle. Biophysical characterization by SDS-PAGE, gel permeat ion chromatography and by electron microscopy of negatively stained si ngle molecules demonstrated that, similar to other vertebrate Mi-CKs, human sarcomeric Mi-CK occurs in two different oligomeric forms, dimer s and octamers, that are readily interconvertible. The apparent M(r)s of Mi-CK protomers, dimers and octamers were 43 600 +/- 800, 79 700 +/ - 800 and 371 000 +/- 3 000, respectively. In addition, isoelectric fo cussing proved to be a suitable technique for routinely distinguishing Mi-CK from cytosolic MM-CK and gave pI values of 8.30 +/- 0.04 and 7. 44 +/- 0.04 for octameric and dimeric human sarcomeric Mi-CK. Circumst antial evidence suggests that both the highly symmetrical structure an d the high pI value of Mi-CK octamers are crucial determinants for the physiological functions of this enzyme. (C) 1997 Academic Press Limit ed.