L-PIPECOLIC ACID METABOLISM IN HUMAN LIVER - L-ALPHA-AMINOADIPATE DELTA-SEMIALDEHYDE OXIDOREDUCTASE

A soluble enzyme that catalyzes the oxidation of l-α-aminoadipate δ-emialdehyde to l-α-aminoadipic acid in the presence of NAD+ has been isolated and characterized from human liver. This enzyme l-α-aminoadipic δ-semialdehyde oxidoreductase has been found to be localized in the cytosol using subcellular fractionation and marker enzyme assays. The reaction product of this enzyme has been identified as l-α-aminoadipic acid by use of an amino acid analyzer and thin layer chromatography. The enzymatic reaction was irreversible and has a pH optimum of 8. The enzyme was stimulated by Mg2+, Cu2+ and Mn2+, and has a requirement of free -SH groups. The Km and Vmax values for its substrate l-α-aminoadipate δ-semialdebyde were shown to be 181 μM and 71.4 pmol·min-1·mg-1, respectively, and for its coenzyme NAD+ to be 454 μM and 142.9 pmol·min-1·mg-1, respectively. The characteristics of the oxidoreductase obtained from the human liver and Pseudomonan putida were compared. © 1990.