The taurine biosynthetic pathway of microalgae

Taurine (2-aminoethanesulfonic acid) is an amino acid-like compound widely distributed in animals and an essential nutrient in some species. Targeted metabolomics of marine and fresh water microalgae combined with medium supplementation identified biosynthetic pathway intermediates and necessary catalytic activities. Genomic analysis was then used to predict the first taurine biosynthetic pathway in these organisms. MRM-based electrospray ionization (ESI) LC-MS/MS analysis demonstrated that taurine is synthesized using a carbon backbone from l-serine combined with sulfur derived from sulfate. Metabolite analysis showed a non-uniform pattern in levels of pathway intermediates that were both species and supplement-dependent. While increased culture salinity raised taurine levels modestly in marine alga, taurine levels were strongly induced in a fresh water species implicating taurine as an organic osmolyte. Conservation of the synthetic pathway in algae and metazoans together with a pattern of intermittent distribution in other lineages suggests that it arose early in eukaryotic evolution. Elevated levels of cell-associated taurine in algae could offer a new and biorenewable source of this unusual bioactive compound.