Purification From Human Brain and Some Properties of Two Nadph‐linked Aldehyde Reductases Which Reduce Succinic Semialdehyde to 4‐hydroxybutyrate

Two NADPH‐linked aldehyde reductases (alcohol:NADP+oxidoreductase, EC 1.1.1.2) capable of reducing succinic semialdehyde to the anaesthetic Chydroxybutyrate have been purified from human brain to electrophoretic homogeneity. The first of these enzymes, which is typical of its category, is not specific for succinic semialdehyde and can reduce some aromatic aldehydes at a high rate. It is a monomer of molecular weight about 45,000 and is strongly inhibited by various hypnotics and anticonvulsants. The second enzyme is, in contrast, fairly specific for succinic semialdehyde. It is a dimer of molecular weight about 90,000 and is not inhibited by the hypnotics and anticonvulsants which inhibit the first enzyme. It is thus different from previously described aldehyde reductases from human brain.