The coenzyme-binding characteristics of highly purified preparations of sheep liver cytoplasmic aldehyde dehydrogenase.

The binding of NADH and NAD+ by cytoplasmic aldehyde dehydrogenase was studied by various direct and indirect methods. At pH 7.0 at 25 degrees C there appears to be approx. 1 binding site for both nucleotides per 200 000 daltons of protein, although the NAD+-binding results are rather uncertain. Estimates of the dissociation constants of the E . NADH and E . NAD+ complexes under the stated conditions are also presented. Preparations of enzyme are sometimes found to contain significant amounts of very tightly bound NAD+ and NADH. The implications of these findings are discussed.