Purification and Properties of α-Amino-β-Carboxymuconate-ε-Semialdehyde Decarboxylase (ACMSD), Key Enzyme of Niacin Synthesis from Tryptophan, from Hog Kidney

Abstract

α-Amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) (EC 4.1.1.45) was purified to a homogeneous state from hog kidney cytosol by ammonium sulfate fractionation, Butyl-Toyopearl 650, hydroxyapatite, DEAE-Sephadex, Toyopearl HW55, Superdex 200 and TSK-gel G3000SW chromatographies. The molecular weight of the enzyme was estimated to be 58, 000 by TSK-gel G3000SW gel filtration. The optimum pH (constant concentration) was 7.5. The K_m for α-amino-β-carboxymuconate-ε-semialdehyde was 1.61×10^-5M. The activity of purified enzyme was inhibited by some chemical modifying reagents such as monoiodoacetic acid and p-(chloromercuri)benzoic acid. A sulfhydryl group was deduced to exist in the active site of the enzyme.