CANTHAXANTHIN BIOSYNTHESIS BY THE CONVERSION OF METHYLENE TO KETO GROUPS IN A HYDROCARBON BETA-CAROTENE BY A SINGLE-GENE

Compounds that include (a) keto group(s) in a molecule are ubiquitous natural components. A novel gene involved in ketocompound biosynthesis , designated crtW, was isolated from the marine bacteria Agrobacterium aurantiacum and Alcaligenes PC-1 that produce ketocarotenoids such as astaxanthin. When this gene was introduced into Escherichia coli that accumulated beta-carotene due to the Erwinia carotenogenic genes, the E. coli transformants synthesized canthaxanthin, one of ketocarotenoi ds, which was identified after purification by its visible, FD-MS and IH-NMR spectral analysis. It has been demonstrated for the first time that one gene encodes an enzyme ''ketolase'' that catalyzes the conver sion of methylene groups of a hydrocarbon beta-carotene to keto groups for synthesizing canthaxanthin via echinenone. (C) 1995 Academic Pres s, Inc.