title: Studies on phosphoglyceromutase from chicken breast muscle: chemical modification of lysyl residues.
abstract: To examine the role of lysyl residues in the activity of the enzyme, phosphoglyceromutase (PGM) from chicken breast muscle was chemically modified with trinitrobenzenesulfonate (TNBS) and pyridoxal 5'-phosphate. Trinitrophenylation resulted in modification of about nine lysines per mole of PGM with almost complete activity loss. Substrate (3-PGA) offered some protection to TNBS inactivation but cofactor (2,3-DPGA) did not. Reduction of the Schiff's base complex between pyridoxal 5'-phosphate and PGM gave irreversible inactivation of the enzyme. Inactivation was due to incorporation of 1 mol of pyridoxal 5'-phosphate per mole of PGM dimer through the epsilon-amino group of a lysyl residue. The effect of pyridoxal 5'-phosphate was specific for intact native enzyme and reaction with only one lysine per dimer was not due to induced conformational changes nor to dissociation of the reacted enzyme. 3-PGA prevented much of the reaction with pyridoxal 5'-phosphate with preservation of 70% of the activity and was a competitive inhibitor of the active site directed reagent. Cofactor (2,3-DPGA) acting noncompetitively, reduced the rate at which inactivation occurred with pyridoxal 5'-phosphate. Incorporation of 2,3-[32P]DPGA into PGM irreversibly inactivated with pyridoxal 5'-phosphate and NaBH4 was incomplete indicating hindrance to phosphorylation in the modified enzyme. The results indicate that a lysyl residue is located at or near the active site of PGM and that it is probably involved in the binding of 3-PGA.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002645:Chickens; D002942:Circular Dichroism; D007700:Kinetics; D008239:Lysine; D009132:Muscles / Q000201:enzymology*; D009578:Nitrobenzenes / Q000494:pharmacology*; D010736:Phosphoglycerate Mutase / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D013056:Spectrophotometry, Ultraviolet; D014302:Trinitrobenzenesulfonic Acid / Q000494:pharmacology*
chemical_list: D009578:Nitrobenzenes; D011732:Pyridoxal Phosphate; D014302:Trinitrobenzenesulfonic Acid; D010770:Phosphotransferases; D010736:Phosphoglycerate Mutase; D008239:Lysine