Biochemical Characterization of ß-Amino Acid Incorporation in Fluvirucin†B2 Biosynthesis.

Naturally occurring lactams, such as the polyketide-derived macrolactams, provide a diverse class of natural products that could enhance existing chemically produced lactams. Although ß-amino acid loading in the fluvirucin B2 polyketide pathway was proposed by a previously identified putative biosynthetic gene cluster, biochemical characterization of the complete loading enzymes has not been described. Here we elucidate the complete biosynthetic pathway of the ß-amino acid loading pathway in fluvirucin B2 biosynthesis. We demonstrate the promiscuity of the loading pathway to utilize a range of amino acids and further illustrate the ability to introduce non-native acyl transferases to selectively transfer ß-amino acids onto a polyketide synthase (PKS) loading platform. The results presented here provide a detailed biochemical description of ß-amino acid selection and will further aid in future efforts to develop engineered lactam-producing PKS platforms.