Degradation of fumonisin B1 by the consecutive action of two bacterial enzymes

Abstract

Detoxification of the mycotoxin fumonisin B1 comprises at least two enzymatic steps, an initial deesterification reaction, followed by deamination of the resulting hydrolyzed fumonisin B1. In this study, two genes that are responsible for degradation of fumonisin B1 by the bacterium Sphingopyxis sp. MTA144 were identified within a gene cluster, assumed to be associated with fumonisin degradation. The first gene encodes a protein which shows similarity to carboxylesterases, type B. The second gene encodes a polypeptide homologous to aminotransferases, class III. The two genes were isolated and expressed heterologously. The effect of the recombinant enzymes on fumonisin B1 and hydrolyzed fumonisin B1 was determined. The recombinant carboxylesterase was shown to catalyze the deesterification of fumonisin B1 to hydrolyzed fumonisin B1. The heterologously expressed aminotransferase was shown to deaminate hydrolyzed fumonisin B1 in the presence of pyruvate and pyridoxal phosphate. We propose that the consecutive action of these two enzymes is sufficient for fumonisin B1 detoxification. The results of this work provide a basis for the development of an enzymatic detoxification process for fumonisin B1 in food and animal feed, especially under oxygen limited conditions, as they are found, e.g. in ensilaged forage or in the intestinal tract of animals.