Stable isotope and chemical inhibition analyses suggested the existence of a non-mevalonate-like pathway in the yeast Yarrowia lipolytica.

Methyl erythritol phosphate (MEP) is the metabolite found in the MEP pathway for isoprenoid biosynthesis, which is known to be utilized by plants, algae, and bacteria. In this study, an unprecedented observation was found in the oleaginous yeast Yarrowia lipolytica, in which one of the chromatographic peaks was annotated as MEP when cultivated in the nitrogen limiting condition. This finding raised an interesting hypothesis of whether Y. lipolytica utilizes the MEP pathway for isoprenoid biosynthesis or not, because there is no report of yeast harboring the MEP pathway. Three independent approaches were used to investigate the existence of the MEP pathway in Y. lipolytica; the spiking of the authentic standard, the MEP pathway inhibitor, and the 13C labeling incorporation analysis. The study suggested that the mevalonate and MEP pathways co-exist in Y. lipolytica and the nitrogen limiting condition triggers the utilization of the MEP pathway in Y. lipolytica.

Identification of biosynthetic genes for the ß-carboline alkaloid kitasetaline and production of the fluorinated derivatives by heterologous expression.

ß-Carboline alkaloids exhibit a broad spectrum of pharmacological and biological activities and are widely distributed in nature. Genetic information on the biosynthetic mechanism of ß-carboline alkaloids has not been accumulated in bacteria, because there are only a few reports on the microbial ß-carboline compounds. We previously isolated kitasetaline, a mercapturic acid derivative of a ß-carboline compound, from the genetically modified Kitasatospora setae strain and found a plausible biosynthetic gene cluster for kitasetaline. Here, we identified and characterized three kitasetaline (ksl) biosynthetic genes for the formation of the ß-carboline core structure and a gene encoding mycothiol-S-conjugate amidase for the modification of the N-acetylcysteine moiety by using heterologous expression. The proposed model of kitasetaline biosynthesis shows unique enzymatic systems for ß-carboline alkaloids. In addition, feeding fluorotryptophan to the heterologous Streptomyces hosts expressing the ksl genes led to the generation of unnatural ß-carboline alkaloids exerting novel/potentiated bioactivities.