title: Inactivation and degradation of yeast glucose-6-phosphate dehydrogenase selectively modified by pyridoxal-5-phosphate.
abstract: Modification by pyridoxal-5-phosphate of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) purified from Saccharomyces cerevisiae produces an inactivation effect, partially reversible by dilution in the presence of substrates. Spectroscopic analysis of the enzyme pyridoxal-5-phosphate complex reduced with NaBH4 provides the values expected for the binding of the aldehydic group to Lys residue. One Lys residue appears to be responsible for the observed enzyme inactivation, and the presence of the phosphate group is required for the effect. Besides the change of activity, the binding of pyridoxal-5-phosphate to the enzyme causes an increase in susceptibility to degradation by the intracellular yeast proteinase A at pH 7.6.
mesh_terms: D016282:Aspartic Acid Endopeptidases; D001665:Binding Sites; D010450:Endopeptidases / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013053:Spectrophotometry
chemical_list: D011732:Pyridoxal Phosphate; D005954:Glucosephosphate Dehydrogenase; D010450:Endopeptidases; C022325:aspartic proteinase A; D016282:Aspartic Acid Endopeptidases