title: Sensitive assay of creatine kinase isoenzymes in human serum using M subunit inhibiting antibody and firefly luciferase.
abstract: A sensitive method for the assay of B subunit and total creatine kinase activity is described. The ATP formation in the creatine kinase reaction is continuously monitored by measuring the bioluminescence obtained with a purified firefly luciferase reagent. The B subunit activity is determined using an M subunit inhibiting antibody resulting in greater than 99.5% and approximately 50% inhibition of MM and MB isoenzymes, respectively. The bioluminescent method correlated well with a similar spectrophotometric method in the assay of B subunit as well as total creatine kinase activity (r greater than or equal to 0.98). However, the bioluminescent assay is considerably more sensitive, allowing the assay of B subunit activity in serum from healthy individuals. This is due to the inherent sensitivity of the bioluminescent assay of ATP, a reduced analytical interference from adenylate kinase and a reduced reagent blank. The within-series precision at 1 U/liter and greater than 52 U/liter corresponded to a C.V. of 14% and 3%, respectively. The method is as rapid and suitable for routine work as spectrophotometric methods. From a clinical point of view the new method is of particular interest in the early diagnosis of small acute myocardial infarctions.
mesh_terms: D000263:Adenylate Kinase / Q000097:blood; D000906:Antibodies; D001667:Binding, Competitive; D001517:Coleoptera; D003402:Creatine Kinase / Q000097:blood* / Q000276:immunology; D005069:Evaluation Studies as Topic; D006801:Humans; D007527:Isoenzymes / Q000097:blood* / Q000276:immunology; D008156:Luciferases; D008163:Luminescent Measurements; D013053:Spectrophotometry
chemical_list: D000906:Antibodies; D007527:Isoenzymes; D008156:Luciferases; D003402:Creatine Kinase; D000263:Adenylate Kinase