Characterization of Zeaxanthin glucosylase (CrtX) from Paracoccus haeundaensis

Zeaxanthin, one of the carotenoids, is found most abundantly in dark, leafy green vegetables and crucial to the good health of the eyes. We have previously reported the isolation of a new marine bacterium, Paracoccus haeundaensis, which produces carotenoids, mainly astaxanthin. The astaxanthin biosynthesis gene cluster from the P. haeundaensis, consisting of six carotenogenic genes, was cloned and their molecular characteristics were previously reported. Zeaxanthin glucosyltransferase (CrtX) mediates the formation of zeaxanthin to zeaxanthin diglucoside. In the present study, zeaxanthin glucosyltransferase gene (crtX) was isolated from the marine bacterium, Paracoccus haeundaensis, and consisted of 1248 bp encoding 415 amino acids residues. The nucleotide sequence of crtX was analyzed and turned out to be well conserved during evolution. The expression plasmid containing crtX gene (pSTCRT‐X) was constructed and E. coli cells containing this plasmid produced the recombinant protein of approximately 46 kDa, which corresponds to zeaxanthin glucosyltransferase. The biosynthesis of zeaxanthin diglucoside was obtained when pSTCRT‐X plasmid was co‐transformed into the E. coli containing the plasmid pET‐44a(+)‐CrtEBIYZ carrying the astaxanthin biosynthesis genes (crtE, crtB, crtI, crtY, and crtZ) from the P. haeundaensis required for zeaxanthin β‐D‐diglucoside biosynthesis.