Aims/background-In humans there are three
phosphoglycerate mutase (PGM, EC 5.4.12.1)
isoenzymes (MM, MB and BB) which have similar distribution and developmental pathways to
creatine kinase (CK, EC 2.7.3.2)
isoenzymes. Total serum PGM activity increases in acute
myocardial infarction with the same time course as
creatine kinase activity. The present study was undertaken to determine changes in the activity of PGM and its
isoenzymes after acute
myocardial infarction.Methods-PGM activity was measured spectrophotometrically, by coupling the formation of
2-phosphoglycerate from
3-phosphoglycerate with
enolase,
pyruvate kinase and
lactate dehydrogenase catalysed reactions. Inter- and intra-assay reproducibility was assessed. PGM
isoenzyme activities were measured using
cellulose acetate electrophoresis.Results-Total PGM activity in serum was increased in patients with a confirmed diagnosis of acute
myocardial infarction. PGM activity peaked 12 to 24 hours after the onset of symptoms and returned to normal values within 48 hours. Electrophoretic analysis of serum from healthy subjects showed a band corresponding to BB-PGM and two other artefactual bands that did not correspond to
adenylate kinase. After
myocardial infarction, BB-PGM activity increased and MB-PGM and MM-PGM could be detected. On immunoblot analysis, normal serum contained an inactive form of MM-PGM with a smaller molecular weight than that of PGM tissue
isoenzymes.Conclusions-Total serum PGM activity increased in patients with acute
myocardial infarction, following the same temporal course as
creatine kinase activity. The increase in MM-PGM and MB-PGM activities in these patients was not as high as expected. It is suggested that PGM
isoenzymes, after release into the blood, undergo postsynthetic, probably proteolytic, transformation.