Heterogeneity of NADPH‐Dependent Aldehyde Reductase from Human and Rat Brain

1 Four multiple molecular forms of NADPH‐dependent aldehyde reductase are isolated by ion‐exchange and gel chromatography from human brain. Using the same procedure two multiple forms of NADPH‐dependent aldehyde reductase are found in rat brain. 2 The molecular weight of two of the forms of human brain aldehyde reductase is 40000 and of the other two forms it is 44000. 3 Large differences with respect to substrate specificity with a wide range of aliphatic and aromatic aldehydes are observed between the multiple enzyme forms of each species. 4 All enzyme forms use NADPH as coenzyme; additionally one enzyme of each species can use NADH as well. 5 Classical inhibitors of aldehyde and alcohol dehydrogenase do not affect the activity of the multiple molecular forms of aldehyde reductase from human and rat brain, but psychoactive substances such as barbiturates and chlorpromazine as well as “biogenic” acids are inhibitory.