CLONING AND EXPRESSION IN ESCHERICHIA-COLI OF THE GENE ENCODING BETA-C-4-OXYGENASE, THAT CONVERTS BETA-CAROTENE TO THE KETOCAROTENOID CANTHAXANTHIN IN HAEMATOCOCCUS-PLUVIALIS

In the green alga Haematococcus pluvialis the ketocarotenoid astaxanth in accumulates under stress conditions, Astaxanthin is a red carotenoi d pigment which possess antioxidative activity. We have cloned the gen e for beta-C-4 oxygenase (beta-carotene ketolase) from the green algae H. pluvialis. The cloning method took advantage of a strain of E. col i which was genetically engineered to produce beta-carotene. An expres sion cDNA library of H. pluvialis was transfected to cells of this str ain and visually screened for brown-red pigmented colonies, One colony out of 100,000 transformants showed color change due to accumulation of canthaxanthin. The cDNA clone in this transformant colony encodes t he enzyme beta-C-4 oxygenase that catalyzes the conversion of beta car otene to canthaxanthin via echinenone. This enzyme does not convert ze axanthin to astaxanthin, It is concluded that in H. pluvialis astaxant hin is synthesized via canthaxanthin and therefore an additional enzym e is predicted, which converts canthaxanthin to astaxanthin.