Yeast glyceraldehyde-3-phosphate dehydrogenase: evidence that subunit cooperativity in catalysis can be controlled by the formation of a complex with phosphoglycerate kinase

摘要: Sepharose-bound tetrameric, dimeric and monomeric forms of yeast glyceraldehyde-3-phosphate dehydrogenase were prepared, as well immobilized hybrid species containing (by selective oxidation an active center cysteine residue with H2O2) one inactivated subunit per tetramer or dimer. The catalytic properties these enzyme compared in the forward reaction (glyceraldehyde-3-phosphate oxidation) reverse (1,3-bisphosphoglycerate reductive dephosphorylation) under steady-state conditions. In oxidation, tetrameric exhibited similar specific activities. hybrid-modified dimer contributed half total activity a native modified possessed 75% unmodified tetramer. In 1,3-bisphosphoglycerate dephosphorylation, was nearly twice high that tetramer, suggesting only one-half centers oligomer acting simultaneously. Subunit cooperativity catalysis persisted isolated species. monomer associated peroxide-inactivated equal to subunits did not differ from tetramer; this indicates interdimeric interactions are involved cooperativity. A complex formed between soluble phosphoglycerate kinase. Three monomers kinase bound Evidence is presented if dephosphorylation proceeds – complex, all sites latter act independently, i. e. abolished.