Further Investigation of the Enzymatic Pathway for Microcystins Biodegradation by Sphingopyxis sp.USTB-05

Based on the isolation of a promising bacterial strain of Sphingopyxis sp. USTB-05 for biodegrading MCs, the genes USTB-05-A (HM245411), USTB-05-B (KC513423) and USTB-05-C (KC573527) that are responsible for the biodegradation of MCs were cloned and expressed for the first time. After purification, the MC-degrading enzymes encoded by these genes were used for the catalytic degradation of MC-LR. The results demonstrated that the second enzyme encoded by USTB-05-B could convert linear MC-LR to a tetrapeptide by breaking the Ala–Arg bond. The third enzyme encoded by USTB-05-C could cleave Adda-Glu peptide bonds of both linear MC-LR and the tetrapeptide of Adda-Glu-Mdha-Ala, producing Adda as their common product. These findings will help better understand the biodegradation mechanism of MCs by Sphingopyxis sp. USTB-05.