Related Experiment Video
Updated: Mar 14, 2026

Chemical Modification of the Tryptophan Residue in a Recombinant Ca2+-ATPase N-domain for Studying Tryptophan-ANS FRET
Published on: October 9, 2021
Essential residues in angiotensin converting enzyme: modification with 1-fluoro-2,4-dinitrobenzene
P Bünning1, S G Kleemann, J F Riordan
1Center for Biochemical and Biophysical Sciences and Medicine, Harvard Medical School, Boston, Massachusetts 02115.
Abstract:
The peptidase and esterase activities of rabbit pulmonary angiotensin converting enzyme (ACE) are rapidly abolished on reaction with 1-fluoro-2,4-dinitrobenzene (Dnp-F). Inactivation follows first-order kinetics with respect to the reagent and is accompanied by stoichiometric incorporation of 3,5-[3H]Dnp, indicating that the effect is due to a specific modification of the enzyme. Thin-layer chromatography of an acid hydrolysate of the modified enzyme indicates that most of the radioactive label is present as O-Dnp-tyrosine (65 to greater than 95%) and the rest as N epsilon-Dnp-lysine. The pH dependence of the reaction is consistent with modification of either tyrosine or lysine. The presence of a competitive inhibitor effectively protects the enzyme against inactivation by Dnp-F. Acetylation of ACE with N-acetylimidazole also protects the enzyme against modification with Dnp-F. The results indicate the presence of catalytically essential tyrosine and lysine residues at the active site of ACE.
Related Concept Videos
Antihypertensive Drugs: Angiotensin-Converting Enzyme Inhibitors
Electrophilic Aromatic Substitution: Nitration of Benzene
Nucleophilic Aromatic Substitution: Elimination–Addition
2° Amines to N-Nitrosamines: Reaction with NaNO2
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo,...

