Properties of non-homologous salicylate hydroxylases of pseudomonus bacteria

Abstract

The non-homologous salicylate hydroxylases NahG and NahU of the strains Pseudomonas fluorescens 142 NF and P. putida BS3701 were extracted and purified by ion-exchange and hydrophobic and gel permeation chromatography. The purified enzymes differed in kinetic and catalyst characteristics during salicylate hydrolysis. For NahU salicylate hydroxylase, Km and Vmax were found to be higher (3.1 ± 0.6 μM and 7.7 ± 0.4 μM/min, respectively) than for NahG salicylate hydroxylase (1.3 ± 0.1 μM and 4.7 ± 0.1 μM/min, respectively). The activity of both enzymes toward substituted salicylates was higher in cases where the substituent groups were in para-position than in cases with those in meta-position. The activity toward substituted salicylates with substituent groups in meta position was different. The activity of salicylate hydroxylase NahG was higher toward salicylates with substituent groups in position 3; salicylate hydroxylase NahU activity was higher toward those with substituent groups in position 5. This suggests about a difference in the spatial configuration of active sites of the purified non-homologous salicylate hydroxylases.