A comparison of enzyme activity for energy production in the myocardium and conduction system.

Specific activities of enzymes in bovine hearts were measured. The enzyme activity ratios between the conduction system and the myocardium were 1.9 for G-6-PDH, 1.2 for PFK, 0.5 for total phosphorylase and LDH, 0.4 for GOT and MDH, 0.3 for SDH, 0.2 for Aldolase and CPK, and 0.1 for alpha GPDH. Approximate values for relative volume of Purkinje cells, nerve fibers and connective tissues in the conduction system were 30%, 8%, and 62%, respectively. It is concluded that activities of enzymes serving for anaerobic glycolysis in Purkinje cells are almost the same or slightly higher than those in the myocardium, and activity of enzyme for pentose shunt in the conductive tissue is higher than that in the myocardium.