Open AccessNuclear magnetic relaxation studies of the role of the metal ion in Mn 2+ ‐substituted aminoacylase I
Author(s) -
HEESE Dirk,
BERGER Stefan,
RÖHM KlausHeinrich
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb15385.x
Subject(s) - chemistry , paramagnetism , ligand (biochemistry) , relaxation (psychology) , metal , metal ions in aqueous solution , proton , kinetic energy , substrate (aquarium) , ion , crystallography , catalysis , active site , stereochemistry , biochemistry , organic chemistry , psychology , social psychology , physics , receptor , oceanography , quantum mechanics , geology
Substitution of the essential Zn 2+ ions of porcine kidney aminoacylase I (EC 3.5.1.14) by Mn 2+ did not markedly affect the kinetic properties of the enzyme. Using Mn 2+ as a paramagnetic probe, we were able to study the conformations of bound ligand by measuring the enhancement of ligand proton relaxation in 1 H NMR. In addition, the effects of inhibitors on the paramagnetic enhancement of water proton relaxation rates were examined. The results of both approaches, in agreement with kinetic evidence, suggest that the metal center of aminoacylase I is too distant from the ligand binding site to allow direct participation of the metal in substrate binding or catalysis. We, therefore, propose that the metal ion of aminoacylase I plays a purely structural role.