Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The biosynthetic pathway for staphyloxanthin, a C30 carotenoid biosynthesized by Staphylococcus aureus, has previously been proposed. Here, we report on the identification of a missing enzyme, 4,4’-diaponeurosporen-aldehyde dehydrogenase, in staphyloxanthin biosynthesis by a synthetic biological approach and propose a complete staphyloxanthin biosynthetic pathway. When we expressed the known pathway genes in artificial synthetic operons and the wild-type operon CrtOPQMN in a heterologous host, Escherichia coli, some pathway intermediates, such as 4,4’-diaponeurosporen-4-al and 4,4’-diapolycopene-dial, were produced without staphyloxanthin or similar structures. We then searched for aldehyde dehydrogenases catalyzing the oxidation of the aldehyde to carboxylic acid and found that one aldehyde dehydrogenase, ald, from S. aureus catalyzed the further oxidation, from aldehyde to carboxylic acid, on both ends of 4,4’-diapolycopene-dial. With the identification of the sixth pathway enzyme, ald, and the staphyloxanthin-like compounds, which contain altered fatty acid acyl chains, the complete biosynthetic pathway of staphyloxanthin was elucidated.