The beta enolase subunit displays three different patterns of microheterogeneity in human striated muscle

In higher vertebrates, the glycolytic enzyme enolase (2-phospho-D-glycerate hydrolyase; EC 4.2.1.11) is active as a dimeric protein formed from three subunits - alpha: ubiquitous, beta: muscle specific, and gamma: neuron spec ific - encoded by different genes. In the present study, we have shown that an antiserum previously produced against the mouse beta beta enolase is al so a specific reagent for the muscle specific human enolase. Using this ant iserum to study human muscles, we demonstrated novel patterns of the beta s ubunit microheterogeneity which are distinctive from those observed previou sly in rodents and which appear to be independent of age, gender and muscul ar activity. Two variants of the beta subunit differing by their size have been detected: one heavy form of 46 kDa (beta H) and one light form of 45 k Da (beta L). Muscle biopsies expressed either beta H or beta L or beta H beta L, and all muscles of an individual expressed the same variants. The p roducts of in vitro translation of RNA prepared from human muscle displayed beta subunit variants identical to those of the protein present in the bio psy. Therefore the differences observed between individuals reveal a differ ence already present at the level of the RNA transcripts. These observation s suggest the existence of an yet undescribed polymorphism of the human bet a enolase gene which could affect the coding sequence. Comparative immunocy tochemical and histochemical analyses of biopsies demonstrated that the bet a subunit was expressed in all fast fibres (type II), but not in slow fibre s (type I). No difference was observed in the intensity of beta enolase imm unolabelling between the various types (IIA, IIAB, TIE) of fast fibres. No significant difference in fibre type composition and histological appearanc e was visible between muscles presenting either one of the three patterns o f microheterogeneity.