Analytical patterns and biochemical properties of macro creatine kinase type 2.

Here we describe our findings for 105 patients' sera containing macro creatine kinase (CK) type 2, as confirmed by exclusion chromatography. Depending on the technique used for determining isoenzyme CKs (electrophoresis, ion-exchange chromatography, immunoinhibition), this variant CK shows characteristic patterns and interferes in CK-MB assays by different mechanisms and to various degrees, thus complicating test interpretation. Macro CK type 2 evidently is not of cytoplasmic origin; rather it is a separate CK activity of human serum, characterized by its heat stability and, especially, by its increased molecular mass and high energy of activation. These latter characteristics have never been associated with the normal-size, dimeric cytoplasmic CK isoenzymes, but are typical for mitochondrial CK isolated from human tissues. We conclude that mitochondrial CK released after severe cell damage usually appears in blood in macromolecular forms (macro CK type 2), not in a dimeric form.