Purification of the high-Km aldehyde reductase from rat brain and liver and from ox brain.

A procedure is described that yields an apparently homogeneous preparation of the high-Km aldehyde reductase from rat brain. This procedure is also applicable to the purification of this enzyme from rat liver and ox brain. In the latter case, however, the purified preparation could be resolved into two protein bands, both of which had enzyme activity, by polyacrylamide-gel electrophoresis. Since a sample of the ox brain enzyme from an earlier step in the purification procedure only showed the presence of a single band of activity after electrophoresis, this apparent multiplicity probably results from modification of the enzyme, possibly by oxidation, during the final step of the purification. A number of properties of the rat brain enzyme were determined and these were compared with those of the enzyme from rat liver. The two preparations were similar in their stabilities, behaviour during purification, kinetic properties, electrophoretic mobilities and amino acid compositions. Antibodies to the rat liver enzyme cross-reacted with that from brain and the inhibition of both these preparations by the antiserum was similar, further supporting the view that the enzymes from these two sources were closely similar if not identical.