A Soluble Protein Factor from Chinese Cabbage Converts Indole-3-acetaldoxime to IAA

Article abstract of DOI:10.1016/S0031-9422(00)84751-2

A soluble enzyme preparation from Chinese cabbage seedlings (Brassica campestris ssp. pekinensis) which catalyses the conversion of indole-3-acetaldoxime (IAOX) to IAA was partially purified by ion exchange chromatography.After purification enzyme activity was stable for more than 6 hr.Substrate kinetics showed a K_m value of 50 μM; the pH optimum was 7.The conversion of IAOX to IAA was increased by NAD, NADP or FAD, but none of them seemed to be a preferential co-substrate.Besides IAA some labelled indole-3-acetaldehyde (IAALD) could be extracted from the reaction mixture.Addition of unlabelled IAALD at 100 nmol/ml led to a significant inhibition of IAA formation while some label accumulated in the aldehyde.Indole-3-acetonitrile was never detected as a reaction product.The results are compared with those from earlier in vivo experiments and are discussed in view of their significance for IAA biosynthesis in the Brassicaceae.Key Word Index - Brassica campestris ssp. pekinensis; Cruciferae; Chinese cabbage; indole-3-acetaldoxime; indole-3-acetaldehyde; IAA biosynthesis.