The catalytic metal atoms of cobalt substituted liver alcohol dehydrogenase.

Abstract

The catalytic and non-catalytic Zn atom pairs of horse liver alcohol dehydrogenase (LADH) have been replaced sequentially either by 65 Zn, Co or 65 Zn and Co. The Co derivatives exhibit characteristic spectra. When Co replaces the Zn atoms which exchange secondly, enzymatic activity is altered, and both imidazole and 1,10-phenanthroline (OP) significantly modify the spectrum of the catalytic Co atoms. Further, due to the removal of cobalt, the instantaneous and reversible OP inhibition of the native enzyme becomes time-dependent and irreversible. Jointly, these data identify the pair of metal atoms of LADH which exchange secondly under the present conditions as the catalytic one. The approach described provides a basis for the differentiation of catalytic and non-catalytic metal atoms of multichain metalloenzymes.