Electrophoretic characteristics of macro creatine kinase type 2 in serum.

We have studied the electrophoretic characteristics of a creatine kinase (CK, EC 2.7.3.2) isoenzyme, macro creatine kinase type 2 (MCK-2), in the serum of 42 patients with carcinoma of the colon. The patients could be divided into three subgroups by the intensity of the MCK-2 band (nine high, nine medium, and 24 low intensity), but we detected no correlation between the isoenzyme activity and the stage of the cancer. Inhibition of the activity of the CK-M subunit by antibody to CK-M allowed more sensitive detection of MCK-2 in serum and revealed that MCK-2 may be obscured by CK-MM. Moreover, there may be major discrepancies between the amount of MCK-2 seen on electrophoresis and the apparent total CK.