Triphosphopyridine Nucleotide-linked Aldehyde Reductase

Abstract

A broad substrate specificity, low molecular weight, TPNH-linked aldehyde reductase has been purified from the soluble cytoplasm of pig kidney cortex. The enzyme reduces aromatic aldehydes, such as 3-pyridinecarboxaldehyde, 4-nitrobenzaldehyde, 4-carboxybenzaldehyde, and 4-cyanobenzaldehyde; aldoses, such as d -glyceraldehyde, d -lactaldehyde, pyruvaldehyde, and d -glucuronate; and α-diketones, such as (+)-camphorquinone and diacetyl. It also catalyzes a slow TPN-linked oxidation of the corresponding alcohols, as well as Tris. The enzyme, a 30,200 dalton monomer, is homogeneous by gel filtration, ultracentrifugation, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis; but on standard polyacrylamide disc gel electrophoresis it gives multiple bands which have the same relative substrate specificity. A diagnostic property of this reductase is its sensitivity to barbiturate inhibition. Due to its kinetic constants and pH optima, this enzyme probably functions physiologically as an aldehyde reductase rather than an alcohol dehydrogenase. The broad substrate specificity of this reductase overlaps several previously described, apparently unrelated, but perhaps identical, TPN-specific mammalian alcohol dehydrogenases.