Muscle adenylate kinase in Duchenne muscular dystrophy

On the basis of electrophoretic and enzyme inhibition studies it was postulated that an aberrant adenylate kinase occurs in muscle and serum of patients with Duchenne muscular dystrophy (Schirmer, R.H. and Thuma, E. (1972) Biochim. Biophys. Acta 268, 92-97; Hamada, M. et al. (1981) Biochim. Biophys. Acta 660, 227-237; Hamada et al. (1985) J. Biol. Chem. 260, 11595-11602). On the basis of the following results we conclude that Duchenne muscular dystrophy patients do not possess an unusual adenylate kinase isoenzyme. In muscle biopsies from five Duchenne patients, the electrophoretic mobility of adenylate kinase and the inhibition of the enzyme by P1, P5-di(adenosine-5')pentaphosphate (Ap5A) was normal. Because of the high SH-group content of the extracts from Duchenne muscle, high concentrations of Ellman's reagent were needed to inhibit adenylate kinase activity in these samples. In Duchenne plasma the adenylate kinase activity was elevated. Like in muscle specimens, the DTNB inhibition curves were shifted to higher reagent concentrations; this was due to a high SH-group content of Duchenne plasma when compared with normal plasma. With respect to inhibition by Ap5A and electrophoretic mobility, Duchenne adenylate kinase in Duchenne plasma behaved like normal muscle adenylate kinase in normal plasma. It was noted that normal muscle adenylate kinase changes its electrophoretic behaviour when mixed with normal or Duchenne plasma. This finding had been considered previously as evidence for the presence of an aberrant adenylate kinase in Duchenne plasma.