Fig. 1
From: High-level de novo biosynthesis of glycosylated zeaxanthin and astaxanthin in Escherichia coli
Biosynthetic pathway of carotenoid glucosides. The biosynthetic pathway: module 1 AHT, including atoB, hmgS and thmgR; module 2 MPPI, including mevk, pmk, pmd and idi; module 3 EBIA, including crtEBI and ispA (Zhang et al. 2018); and module 4 YZX or YZWX, including crtYZX or crtYZWX. Dashed arrow indicates multiple enzymatic steps. The glycosylation of all carotenoids required UDP-glucose (UDP-glc), here we only used zeaxanthin glucosides as representatives. The genes expressed encode the following enzymes: crtY, lycopene beta-cyclase; crtW, β-carotene ketolase; crtZ, β-carotene hydroxylase; crtX, zeaxanthin glucosyltransferase (ZGT). Thicker and thinner arrows represent the higher and lower carbon flux, respectively; gray arrows represent that the metabolites (e.g., β-cryptoxanthin-β-D-glucoside and 3′-hydroxyechinenone-β-D-glucoside) were not detected in our strains