title: Inactivation of rhodanese by pyridoxal 5'-phosphate.
abstract: Pyridoxal 5'-phosphate and other aromatic aldehydes inactivate rhodanese. The inactivation reaches higher extents if the enzyme is in the sulfur-free form. The identification of the reactive residue as an amino group has been made by spectrophotometric determination of the 5'-phosphorylated pyridoxyl derivative of the enzyme. The inactivation increases with pyridoxal 5'-phosphate concentration and can be partially removed by adding thiosulfate or valine. Prolonged dialysis against phosphate buffer also leads to the enzyme reactivation. The absorption spectra of the pyridoxal phosphate - rhodanese complex show a peak at 410 nm related to the Schiff base and a shoulder in the 330 nm region which is probably due to the reaction between pyridoxal 5'-phosphate and both the amino and thiol groups of the enzyme that appear reasonably close to each other. The relationship betweenloss of activity and pyridoxal 5'-phosphate binding to the enzyme shows that complete inactivation is achieved when four lysyl residues are linked to pyridoxal 5'-phosphate.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D011485:Protein Binding; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013466:Sulfurtransferases / Q000037:antagonists & inhibitors*; D013884:Thiosulfate Sulfurtransferase / Q000037:antagonists & inhibitors*
chemical_list: D011732:Pyridoxal Phosphate; D013466:Sulfurtransferases; D013884:Thiosulfate Sulfurtransferase