Abstract
A novel esterase gene, pytH, encoding a pyrethroid-hydrolyzing carboxylesterase was cloned from Sphingobium sp. strain JZ-1. The gene contained an open reading frame of 840 bp. Sequence identity searches revealed that the deduced enzyme shared the highest similarity with many alpha/beta-hydrolase fold proteins (20 to 24% identities). PytH was expressed in Escherichia coli BL21 and purified using Ni-nitrilotriacetic acid affinity chromatography. It was a monomeric structure with a molecular mass of approximately 31 kDa and a pI of 4.85. PytH was able to transform p-nitrophenyl esters of short-chain fatty acids and a wide range of pyrethroid pesticides, and isomer selectivity was not observed. No cofactors were required for enzyme activity.
Highlights
Pyrethroid pesticides are the major class of insecticides used for insect control in agriculture and households as a replacement for more toxic organophosphorus pesticides, and their usage is continuing to grow [10]
Fenpropathrin, cypermethrin, fenvalerate, deltamethrin, permethrin, cyhalothrin, bifenthrin, and 2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropanecarboxylic acid were obtained from Yangnong Chemical Group Co., Ltd., Jiangsu, China. 3-Phenoxybenzaldehyde, p-chloromercuribenzoic acid, diethyl pyrocarbonate (DEPC), iodoacetamide, and phenylmethylsulfonyl fluoride (PMSF) were purchased from Sigma. cis- and trans-permethrin and cis- and trans-cypermethrin were purchased from the Agro-Environment Protection Institute of MOA, China
Based on the results of morphological and physiological characterization and 16S rRNA gene sequence analysis, strain JZ-1 was identified as a Sphingobium sp. strain
Summary
Pyrethroid pesticides are the major class of insecticides used for insect control in agriculture and households as a replacement for more toxic organophosphorus pesticides, and their usage is continuing to grow [10]. Pyrethroid pesticides are degraded by both abiotic and biotic pathways, including photooxidation, chemical oxidation, and biodegradation. Microorganisms play the most important role in degradation of pyrethroids in soils and sediments. Many pyrethroid-degrading microorganisms have been isolated from soils [13, 16, 24, 27]. The major routes of pyrethroid metabolism in pyrethroidresistant insects and pyrethroid-degrading microorganisms include oxidation by cytochrome P450s and ester hydrolysis by carboxylesterases [9]. Carboxylesterases are a family of enzymes that are important in the hydrolysis of a large number of endogenous and xenobiotic ester-containing compounds, such as carbamates, organophosphorus pesticides, and pyrethroids. Strain JZ-1, the cloning and expression of the gene pytH encoding a novel pyrethroid-hydrolyzing carboxylesterase, and the characterization of the purified enzyme We described the isolation and identification of the pyrethroid-degrading Sphingobium sp. strain JZ-1, the cloning and expression of the gene pytH encoding a novel pyrethroid-hydrolyzing carboxylesterase, and the characterization of the purified enzyme
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