title: Labeling of the active site of alpha-chymotrypsin with N-nitroso-N-benzylacetamide and related compounds.
abstract: alpha-Chymotrypsin (CT) is slowly inhibited by N-nitroso-N-benzylacetamide (1) at 25 degrees C. The 13C-NMR spectrum of the hydrolysate of 13C-enriched 1-inhibited CT shows five new signals at 52.33, 44.55, 43.72, 36.79, and 32.90 ppm resulting from alkylation of the side chains and also of amide linkages of the enzyme backbone by benzyl carbocations produced in the active site. The alkylation pattern is different from those observed in the inhibitions of CT with D-N-nitroso-N-[alpha-13C]-benzyl-N'- isobutyrylalaninamide (2a) and D-N-nitroso-N-[alpha-13-C]-benzyl-N'-isobutyrylphenylalaninamide (2b) (White et al. JACS 1990, 112, 1956-1961). The chemical shift data suggest that the 52.33 ppm signal stems from N-benzylglycine, the 36.79 ppm signal from S-benzylcysteine, and the 32.90 ppm signal from 2-benzyltryptophan. A synthesis of the latter compound was developed.
authors.affiliation: Department of Chemistry, Johns Hopkins University Baltimore, Maryland 21218.
authors.forename: M
authors.initials: M
authors.lastname: Li
authors.forename: D F
authors.initials: DF
authors.lastname: Roswell
authors.forename: E H
authors.initials: EH
authors.lastname: White
mesh_terms: D000081:Acetamides / Q000378:metabolism* / Q000494:pharmacology; D000409:Alanine; D044482:Benzeneacetamides; D001593:Benzyl Compounds / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D002918:Chymotrypsin / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009603:Nitroso Compounds / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D010649:Phenylalanine; D013329:Structure-Activity Relationship
chemical_list: D000081:Acetamides; D044482:Benzeneacetamides; D001593:Benzyl Compounds; D009603:Nitroso Compounds; C084066:N-nitroso-N-benzylacetamide; D010649:Phenylalanine; D002918:Chymotrypsin; D000409:Alanine