Enzymatic pathway for biodegrading microcystin LR in Sphingopyxis sp. C-1

• DOI: 10.1016/j.jbiosc.2012.07.004
• Publication Date: 2012-08-09T14:17:41Z
• Authors: Kazuya Shimizu; Hideaki Maseda; Kunihiro Okano; Takumi Kurashima; Yukio Kawauchi; Qiang Xue; Motoo Utsumi; Zhenya Zhang; Norio Sugiura
• Keywords: Cyanobacteria Toxins; Microcystins; Bacterial Toxins; 01 natural sciences; 3. Good health; Sphingomonadaceae; Biodegradation, Environmental; Bacterial Proteins; Genes, Bacterial; Multigene Family; Proteolysis; Escherichia coli; Marine Toxins; 0105 earth and related environmental sciences

The mlr gene cluster consisting of mlrA, mlrB, mlrC, and mlrD is involved in the degradation of the cyanobacterial toxin microcystin. However, it is unclear which degradation intermediates are metabolized by MlrB and MlrC. To address these questions, we constructed recombinant Escherichia coli to overproduce MlrB and MlrC from Sphingopyxis sp. C-1, and determined which intermediates were degraded in cell-free extracts. The cell-free extract containing MlrB degraded linearized microcystin-LR, giving rise to a tetrapeptide. The cell-free extract of MlrC degraded linearized microcystin-LR and also degraded the tetrapeptide to the amino acid Adda. These results indicate that linearized microcystin-LR is degraded by both MlrB and MlrC, and tetrapeptide is degraded by specifically by MlrC in Sphingopyxis sp. C-1.