Regulation Efficacy and Mechanism of the Toxicity of Microcystin-LR Targeting Protein Phosphatase 1 via the Biodegradation Pathway.

Biodegradation is important to regulate the toxicity and environmental risk of microcystins (MCs). To explore their regulation effectiveness and mechanism, typical biodegradation products originating from microcystin-LR (MCLR) were prepared and purified. The protein phosphatase 1 (PP1) inhibition experiment showed the biodegradation pathway was effective in regulating the toxicity of the biodegradation products by extending the biodegradation. With the assistance of molecular docking, the specific interaction between the toxins and PP1 was explored. The MCLR/MCLR biodegradation products combined with PP1 mainly by the aid of interactions related to the active sites Adda5, Glu6, Mdha7, and the ionic bonds/hydrogen bonds between the integral toxin and PP1. As a consequence, the interactions between Mn22+ and Asp64/Asp92 in the catalytic center were inhibited to varying degrees, resulting in the reduced toxicity of the biodegradation products. During the biodegradation process, the relevant key interactions might be weakened or even disappear, and thus the toxicity was regulated. It is worth noting that the secondary pollution of the partial products (especially for Adda5-Glu6-Mdha7-Ala1 and the linearized MCLR), which still possessed the major active sites, is of deep concern.