title: Characterization of the first step involved in enzymatic pathway for microcystin-RR biodegraded by Sphingopyxis sp. USTB-05.
abstract: 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(-1) was completely biodegraded under total protein of 350 mg L(-1) 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.
authors.affiliation: School of Chemical and Biological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China. haiyan@ustb.edu.cn
authors.forename: Hai
authors.initials: H
authors.lastname: Yan
authors.forename: Junfeng
authors.initials: J
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Huasheng
authors.initials: H
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D001673:Biodegradation, Environmental; D015870:Gene Expression; D005798:Genes, Bacterial; D057097:Harmful Algal Bloom; D008387:Marine Toxins; D052998:Microcystins / Q000378:metabolism*; D008969:Molecular Sequence Data; D042301:Sphingomonadaceae / Q000201:enzymology* / Q000235:genetics; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; C063855:microcystin RR