EXPOSURE OF TYROSINE RESIDUES IN PROTEINS .3. REACTION OF CYANURIC FLUORIDE AND N-ACETYLIMIDAZOLE WITH OVALBUMIN CHYMOTRYPSINOGEN AND TRYPSINOGEN

The state of tyrosine residues (accessible or buried) in ovalbumin, chymotrypsinogen, and trypsinogen has been examined with cyanuric fluoride and N-acetylimidazole. Ovalbumin was found to contain five reactive and four unreactive residues. The reactive ones can be subdivided into four classes of reactivity. There are eight N-acetylimidazole-reactive groups. Chymotrypsinogen contains two reactive and two unreactive residues; reactive residues are of two types. There are three N-acetylimidazole-reactive residues. Trypsinogen contains seven reactive and three unreactive residues. The reactive ones can be subdivided into five classes of 2 + 1 + 1 + 1 + 2 residues according to diminishing reactivity. There are five N-acetylimidazole-reactive residues. © 1969, American Chemical Society. All rights reserved.