Estimation of pyruvate dehydrogenase (E1) activity in human skeletal muscle; three cases with E1 deficiency.

Pyruvate dehydrogenase (E1) catalyzes the rate-limiting step of the pyruvate dehydrogenase complex. Since E1 activity of human muscle tissue is low, a sensitive method is needed for diagnostic purposes. Measurement of 14CO2 production from [1-14C]pyruvate provides a specific and sensitive assay for measuring E1 activity. We use as artificial electron acceptor dichlorophenolindophenol (DCPIP) instead of the often applied ferricyanide. The method can be applied to small muscle samples obtained by needle or open biopsy. We prefer to use total homogenate because E1 activities in homogenate are higher than in the corresponding 600-g supernatant of skeletal muscle tissue. Control values in homogenate are higher or of the same order as those reported by others.