Understanding the molecular mechanism of fumonisin esterases by kinetic and structural studies

Fumonisins are sphingolipid-like mycotoxins that cause serious damage by contaminating food and feed. The tricarballylic acid (TCA) units of fumonisin B₁ (FB₁; accounting for 70 % of fumonisin contamination) can be removed by fumonisin B₁ esterase (FE, EC 3.1.1.87) providing a biotechnological FB₁ detoxification possibility. Here, we report the regioselective cleavage of the TCA ester at C6 in the first step of FB₁ hydrolysis and kinetic characterization for two FEs. The low K_M values (4.76-44.3 μM) are comparable to concentrations of environmental contaminations, and the high catalytic efficiencies are promising for practical applications. The X-ray structure of one of the FEs enabled the understanding of the FB₁ hydrolysis at molecular level and revealed an arginine pocket key for substrate binding, and the catalytic role of the glutamate preceding the catalytic serine. Computations showed that this FE is likely capable of detoxifying any fumonisin indicating its potential applicability in food and feed products.