Sk. Wang et al., AN X-RAY-ABSORPTION SPECTROSCOPY STUDY OF THE INTERACTIONS OF NI2+ WITH YEAST ENOLASE, Journal of inorganic biochemistry, 58(3), 1995, pp. 209-221
An x-ray absorption spectroscopy (XAS) study was carried out at pH 7.6
on solutions of Ni2+ and yeast enolase depleted of its physiological
cofactor (Mg2+) in the presence or absence of substrate/product, the v
ery strongly bound competitive inhibitor 2-phosphonoacetohydroxamate a
nd Mg2+. Both ''conformational'' and ''catalytic'' Ni2+ are distorted
octahedral in coordination, in agreement with several spectroscopic st
udies but in contrast to the coordination in the crystal at pH 6.0. Th
e data are consistent with direct coordination of what must be the cat
alytic Ni2+ to the phosphate of the substrate, in agreement with some
previous data but in disagreement with recent interpretations by other
workers. The ligands around the metal ions obtained from the x-ray st
ructure give simulated XAS spectra in good agreement with the observed
spectra.