title: Photoreactive derivative of Kunitz's soybean trypsin inhibitor. Preparation by selective modification of a tryptophan residue and formation of a covalent complex of the modified inhibitor with trypsin.
abstract: The photoreactive arylsulfenyl chloride 2-nitro-4-azidophenylsulfenyl chloride (2,4-NAPS-Cl) has been used for the selective modification of tryptophan in Kunitz's soybean trypsin inhibitor (SBTI). The ultraviolet absorption spectrum and amino acid analysis of 2,4-NAPS-SBTI indicated that only one of the two tryptophans (93 or 117) present in SBTI was modified. CNBr cleavage of 2,4-NAPS-SBTI resulted in two fragments 1-114 and 115-181. Amino acid analysis of the two separated fragments showed that only tryptophan 93 underwent modification. 2,4-NAPS-SBTI fully retained its inhibitory activity against trypsin. The photoaffinity labeling of trypsin with 2,4-NAPS-Cl was performed on tritiated trypsin prepared by reacting bovine trypsin with [3H]-succinimidyl propionate. The covalent attachment of 2,4-NAPS-SBTI to the tritiated trypsin after photolysis was demonstrated by exclusion chromatography on Sephadex G-50 in the presence of guanidine hydrochloride.
mesh_terms: D000345:Affinity Labels; D000596:Amino Acids / Q000032:analysis; D001386:Azides; D007700:Kinetics; D014357:Trypsin / Q000378:metabolism; D014360:Trypsin Inhibitor, Kunitz Soybean; D014361:Trypsin Inhibitors; D014364:Tryptophan
chemical_list: D000345:Affinity Labels; D000596:Amino Acids; D001386:Azides; D014361:Trypsin Inhibitors; C027146:2-nitro-4-azidophenylsulfenyl chloride; D014364:Tryptophan; D014360:Trypsin Inhibitor, Kunitz Soybean; D014357:Trypsin