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Analogues containing the paramagnetic amino acid TOAC as substrates for angiotensin I‐converting enzyme
Author(s) -
de Deus Teixeira Luis Gustavo,
Bersanetti Patrícia Alessandra,
Schreier Shirley,
Carmona Adriana Karaoglanovich,
Nakaie Clovis Ryuichi
Publication year - 2007
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2007.04.058
Subject(s) - electron paramagnetic resonance , chemistry , dipeptide , enzyme , stereochemistry , steric effects , angiotensin ii , amino acid , biochemistry , nuclear magnetic resonance , physics , receptor
The angiotensin I‐converting enzyme (ACE) converts the decapeptide angiotensin I (Ang I) into angiotensin II by releasing the C‐terminal dipeptide. A novel approach combining enzymatic and electron paramagnetic resonance (EPR) studies was developed to determine the enzyme effect on Ang I containing the paramagnetic 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐4‐amino‐4‐carboxylic acid (TOAC) at positions 1, 3, 8, and 9. Biological assays indicated that TOAC 1 ‐Ang I maintained partly the Ang I activity, and that only this derivative and the TOAC 3 ‐Ang I were cleaved by ACE. Quenching of Tyr 4 fluorescence by TOAC decreased with increasing distance between both residues, suggesting an overall partially extended structure. However, the local bend known to be imposed by the substituted diglycine TOAC is probably responsible for steric hindrance, not allowing the analogues containing TOAC at positions 8 and 9 to act as substrates. In some cases, although substrates and products differ by only two residues, the difference between their EPR spectral lineshapes allows monitoring the enzymatic reaction as a function of time.