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J. Biol. Chem., Vol. 258, Issue 4, 2091-2093, Feb, 1983

Octahedral metal coordination in the active site of glyoxalase I as evidenced by the properties of Co(II)-glyoxalase I

S Sellin, LE Eriksson, AC Aronsson and B Mannervik

Co(II)-glyoxalase I has been prepared by reactivation of apoenzyme from human erythrocytes with Co2+. The visible absorption spectrum showed maxima at 493 and 515 nm and shoulders at 465 and 615 nm. The absorption coefficients at 493 and 515 nm were 35 and 33 M-1 cm- 1/cobalt ion, respectively; i.e. 70 and 66 M-1 cm-1 for the dimeric metalloprotein. The product of the enzymatic reaction, S-D- lactoylglutathione, although binding to Co(II)-glyoxalase I, had no demonstrable effect on the visible absorption spectrum, indicating binding outside the first coordination sphere of the metal. The EPR spectrum at 3.9 K was characterized by g1 approximately 6.6, g2 approximately 3.0, and g3 approximately 2.5, and eight hyperfine lines with A1 = 0.025 cm-1. Binding of the strong competitive inhibitor S-p- bromobenzylglutathione to Co(II)-glyoxalase I gave three g values: 6.3, 3.4, and 2.5, indicating a conformational change affecting the environment of the metal ion. Both optical and EPR spectra strongly suggest a high spin Co2+ with octahedral coordination in the active site of the enzyme. The similarities in kinetic properties between native Zn(II)-glyoxalase I and enzyme substituted with Mg2+, Mn2+, or Co2+ is consistent with the view that these enzyme forms have the same metal coordination in the protein.
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				M. Ridderstrom, A. D. Cameron, T. A. Jones, and B. Mannervik Involvement of an Active-site Zn2+ Ligand in the Catalytic Mechanism of Human Glyoxalase I J. Biol. Chem., August 21, 1998; 273(34): 21623 - 21628. [Abstract] [Full Text] [PDF]