Rapid inhibition assay of human serum phosphoglyceric acid mutase isoenzyme activity and application to clinical evaluation of acute myocardial infarction

Phosphoglyceric acid mutase (PGAM; EC 5. 4. 2. 1) is one of the enzymes in the glycolytic pathway. Considering the two types of subunits, the dimeric enzyme molecule can be arranged in the following threee forms: a dimer consisting of two M subunits, PGAM-MM, the "muscle type" isoenzyme; a hybrid dimer consisting of one M subunit plus one B subunit, PGAM-MB, the "myocardial type" isoenzyme; and a dimer consisting of two B subunits, PGAM-BB, the "grain type" isoenzyme. There are no reports of studies of human serum PGAM isoenzyme activity as a marker of acute myocardial infarction (AMI). An inhibition assay of PGAM-B subunit activity using 1 mM potassium tetrathionate at 20°C for 10 minutes to specifically inactivate the M subunit is under investigation. We report here basic studies examining the PGAM isoenzyme activity assay in human serum using that inhibition assay as well as the clinical significance of PGAM isoenzyme activity as a diagnostic marker for AMI. Within-run precision studies yield CVs of 2.5% and 2.4% on mean PGAM activities of 225 U/l and 770 U/l, respectively. The linearity of the PGAM assay was extended to 1500 U/l. The correlation between findings with a PGAM-M subunit and other cardiac markers using plasma from AMI patients was relative (T-CK: r=0.773; CK-MB: r=0.840). We conclude that the PGAM isoenzyme inhibition assay was easy to use and accurate compared with other cardiac markers and conventional parameters such as CK-MB.