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Molecular Characterization and Directed Evolution of a Metagenome-Derived L-Cysteine
Sulfinate  Decarboxylase


Jie Deng1,2small orcid_display_4pp, Qiaofen Wu2small orcid_display_4pp, Hua Gao2small orcid_display_4pp, Qian Ou2small orcid_display_4pp, Bo Wu2small orcid_display_4pp, Bing Yan1*small orcid_display_4pp and Chengjian Jiang1,2*small orcid_display_4pp



1Guangxi Key Laboratory of Mangrove Conservation and Utilization, Guangxi Mangrove Research Center, Guangxi Academy of Sciences, 92 Changqing Rd., Beihai, Guangxi, PR China
2State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Rd., Nanning, Guangxi, PR China




Article history:
Received: July 8, 2017
Accepted: February 8, 2018




Key words:
taurine, L-cysteine sulfinate decarboxylase, metagenomic library, sequential error-prone PCR




Summary:
L-Cysteine sulfinate decarboxylase (CSD, EC 4.1.1.29), the rate-limiting enzyme in taurine synthesis pathway, catalyzes L-cysteine sulfinic acid to form hypotaurine. Identification of the novel CSD that could improve the biosynthetic efficiency of taurine is important. An unexplored decarboxylase gene named undec1A was identified in a previous work through sequence-based screening of uncultured soil microorganisms. Random mutagenesis through sequential error-prone polymerase chain reaction was used in Undec1A. A mutant Undec1A-1180, which was obtained from mutagenesis library, had 5.62-fold higher specific activity than Undec1A at 35 °C and pH=7.0. Molecular docking results indicated that amino acid residues Ala235, Val237, Asp239, Ile267, Ala268, and Lys298 in the Undec1A-180 protein helped recognize and catalyze the substrate molecules of L-cysteine sulfinic acid. These results could serve as a basis for elucidating the characteristics of the Undec1A-1180. Directed evolution technology is a convenient way to improve the biotechnological applications of metagenome-derived genes.



*Corresponding authors:  tel3  +867713239403
                                                   fax2  +86-7713237873
                                                    email3  gxybing@tom.com (Yan), jiangcj0520@gmail.com (Jiang)




Paper was presented at the 7th International Forum on Industrial Bioprocessing - IFIBiop 2017, May 21-24, 2017, Wuxi, PR China