title: Mechanism of inactivation of chymotrypsin by 5-butyl-3H-1,3-oxazine-2,6-dione.
abstract: 5-Butyl-3H-1,3-oxazine-2,6-dione (1) inactivates chymotrypsin. The extent of inactivation is dependent upon the concentration of 1. Upon dilution of the inactivated enzyme, catalytic activity is partially restored. Reactivation is a biphasic process. An initial relatively rapid phase (k = 1.8 X 10(-2) min), whose amplitude is dependent upon the extent of dilution, is observed. Maximally, 60-65% of the catalytic activity can be recovered. The rapid phase is followed by a slow phase (k approximately 1 X 10(-3) min-1). With 1 labeled with 14C at C-2, it was shown that two forms of inactive enzyme are formed, E.1 and E.1'. 14C label is retained in E.1 but is no longer present in E.1'. Presumably, C-2 is lost as CO2. The following reaction sequence is proposed for the inactivation of chymotrypsin: E + 1 in equilibrium E.1 CO2----E.1'----E + 1''. The probable structures of E.1, E . 1', and 1'' are shown in Scheme I in the text.
mesh_terms: D001665:Binding Sites; D002250:Carbon Radioisotopes; D002918:Chymotrypsin / Q000037:antagonists & inhibitors*; D007202:Indicators and Reagents; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D010078:Oxazines / Q000138:chemical synthesis* / Q000494:pharmacology; D011480:Protease Inhibitors / Q000138:chemical synthesis*
chemical_list: D002250:Carbon Radioisotopes; D007202:Indicators and Reagents; D010078:Oxazines; D011480:Protease Inhibitors; C042687:5-butyl-3H-1,3-oxazine-2,6-dione; D002918:Chymotrypsin