Characterization of the first step involved in enzymatic pathway for microcystin-RR biodegraded by Sphingopyxis sp. USTB-05

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• 作者：Hai Yan^a ; ^{haiyan@ustb.edu.cn} ; Junfeng Wang^a ; ^b ; Jian Chen^a ; Wei Wei^a ; Huasheng Wang^a ; Hui Wang^c
• 关键词：Microcystin-RR ; Sphingopyxis sp. ; USTB-05 ; Cloning and expression of gene ; Enzymatic pathway
• 刊名：Chemosphere
• 出版年：2012
• 出版时间：March 2012
• 年：2012
• 卷：87
• 期：1
• 页码：12-18
• 全文大小：1091 K

文摘

Enzymes encoded by genes biodegrading microcystins (MCs) can help reveal the function of genes and biodegradation pathway of MCs. Here the first and important gene (USTB-05-A, 1,008 bp) involved in biodegradation of microcystin-RR (MC-RR) was cloned from Sphingopyxis sp. USTB-05 and firstly expressed in Escherichia coli BL21 (DE3) with an expression vector of pGEX4T-1 successfully. The nucleotide sequences of cloned USTB-05-A possessed 92.5 % homology to that of mlA reported in Sphingomonas sp. strain ACM-3962. The deduced amino acid sequences containing the cleavage sites of 26th (alanine) and 27th (leucine) showed 83 % identical to that of MlrA. The cell-free extract (CE) of recombinant E. coli BL21 (DE3) containing USTB-05-A had high activity for biodegrading MC-RR. Initial MC-RR of 40 mg L^? was completely biodegraded under total protein of 350 mg L^? within 0.25 h. A product derived from MC-RR appeared distinctly with the decrease of MC-RR peak on the profile of HPLC. The product (m/z 1056.5) had molecular weight of 18 higher than that of MC-RR (m/z 1038.7). The findings provided the positive evidences that biodegradation of MC-RR began with the breakage of cyclic MC-RR and then it was converted to linear MC-RR as the first product catalyzed by first enzyme of Sphingopyxis sp. USTB-05.