Enolase isoenzymes: II. Hybridization studies, developmental and phylogenetic aspects

Abstract

1. 1.|Hybridization studies have been carried out in vitro using mixtures of partially purified isoenzymes 1 and 3 of rat enolase (2-phospho- d-glycerate hydrolyase, EC 4.2.1.11). Immunological methods were used to demonstrate the formation of the hybrid. 2. 2.|Immunological analysis of the elution peaks from QAE-Sephadex chromatography of heart enolase indicates the occurrence in vivo of the hybrid enolase 2. 3. 3.|Developmental changes in the proportions of isoenzymes 1, 2 and 3 in heart and skeletal muscle of rat have been studied quantitatively. In both tissues isoenzyme 1 predominates in the foetus, but is partially replaced by 2 and 3 in adult heart and completely by 3 in the adult muscle. 4. 4.|Evidence is given of the binomial distribution of the proportions of the three isoenzymes in the developing heart. 5. 5.|Phylogenetic studies of the immunological properties of enolases from muscle, liver and heart have been carried out. 6. 6.|It is concluded that the three isoenzymes arise from two independent genetic loci and it is suggested that these evolved from a common ancestral gene 200–300 million years ago.