Organ specificity of creatine phosphokinase muscle isoenzyme

Radioimmunoassay of creatine kinase: studies on the skeletal muscle and cardiac muscle enzyme (MM and MB isoenzymes) in serum and neuromuscular tissues

A radioimmunoassay, specific for the isoenzymes of creatine kinase containing the M subunit of the enzyme (MM and MB creatine kinase), was employed to determine total creatine kinase concentrations in serum and neuromuscular tissues independently of the state of activity of the enzyme. This technique provides a method for the detection of inactive enzyme, which could be produced by inhibitors of the enzyme or by mutations involving the active site of the enzyme. A series of experiments were carried out to compare the amount of creatine kinase in various samples as assessed by normal enzyme kinetic procedures and by radioimmunoassay. The two techniques yielded equivalent results in all situations tested. Samples included serum from normal subjects and subjects with genetic and acquired diseases of muscle and also extracts from skeletal and cardiac muscle. Small quantities of immunoreactive enzyme were found in nervous tissue and assessed in terms of the incidence of the M subunit.

Evidence for significant quantities of creatine kinase MM isoenzyme in human brain

The isoenzymes of creatine kinase (ATP: creatine N-phosphotransferase, EC 2.7.3.2) in human brain were studied. Approx. 30% of total creatine kinase activity is due to the MM isoenzyme. The identity of this isoenzyme was confirmed by several techniques and shown not to be of mitochondrial origin.

Screening of malignant hyperthermia susceptible families by creatine phosphokinase measurement and other clinical investigations

We investigated 56 families afflicted with malignant hyperpyrexia. One hundred and twenty-four individuals within these families had had an episode of malignant hyperthermia, of whom we saw seventy-two. Serum creatine phosphokinase (CPK) was statistically higher in affected individuals and in close relatives than in normal volunteers. The magnitude of the serum CPK elevations varied significantly between families. While in some families the serum CPK was clearly elevated in affected individuals, in other families the serum CPK was normal or only moderately or inconsistently raised. In these latter families serum CPK measurement was therfore of little or no value in identifying afflicted members. The incidence of musculoskeletal abnormalities was greater in affected individuals and in close relatives than in the general population. Thus, the concomitant individual belonging to a family known to be susceptible to malignant hyperthermia was a better indicator of the MH trait than was the presence of only one of these parameters. For reasons which we do not fully understand, MHS individuals were found to require fewer anaesthetics than normal persons. The incidence of MH crises within each family fell significantly following investigation, counselling, and issuance of Medic-Alert bracelets.

Quantitation of creatine kinase isoenzymes in human tissues and sera by an immunological method

Antisera against the crystallized creatine kinase isoenzymes from human skeletal muscle (MM) and from human brain (BB) were produced in rabbits. Both the MM and BB isoenzymes were precipitated quantitatively by their homologous antisera. No cross-reaction was observed. Thy hybrid MB from human heart muscle could not be precipitated completely by either of the two antisera. In artificial mixtures the concentrations of individual creatine kinase isoenzymes were determined from the percentage of non-precipitable activity in the supernatant after reaction with each of the antisera. This immunotitration assay was applied to study the quantitative distribution of creatine kinase compared with those determined by electrophoretic analysis. In sera of patients with myocardial infarction, the immunotitration assay allowed the sensitive and rapid quantitation of creatine kinase isoenzymes, especially of the "infarct-specific" hybrid MB, even in sera with low total activity. This indicates that the method is of diagnostic value.