Genetically engineered biosynthetic pathways for nonnatural C₆₀ carotenoids using C₅-elongases and C₅₀-cyclases in...

While the majority of the natural carotenoid pigments are based on 40-carbon (C₄₀) skeleton, some carotenoids from bacteria have larger C₅₀ skeleton, biosynthesized by attaching two isoprene units (C₅) to both sides of the C₄₀ carotenoid pigment lycopene. Subsequent cyclization reactions result in the production of C₅₀ carotenoids with diverse and unique skeletal structures. To produce even larger nonnatural novel carotenoids with C₅₀ + C₅ + C₅ = C₆₀ skeletons, we systematically coexpressed natural C₅₀ carotenoid biosynthetic enzymes (lycopene C₅-elongases and C₅₀-cyclases) from various bacterial sources together with the laboratory-engineered nonnatural C₅₀-lycopene pathway in Escherichia coli. Among the tested enzymes, the elongases and cyclases from Micrococcus luteus exhibited significant activity toward C₅₀-lycopene, and yielded the novel carotenoids C₆₀-flavuxanthin and C₆₀-sarcinaxanthin. Moreover, coexpression of M. luteus elongase with Corynebacterium cyclase resulted in the production of C₆₀-sarcinaxanthin, C₆₀-sarprenoxanthin, and C₆₀-decaprenoxanthin.