Cloning of two carotenoid ketolase genes from Nostoc punctiforme for the heterologous production of canthaxanthin and astaxanthin

摘要

For the heterologous synthesis of keto-carotenoids such as astaxanthin,two carotenoid ketolase genes crtW38 and crtWI48,were cloned from the cyanobacterium,Nostoc punctiforme PCC 73102 and functionally characterized.Upon expression in Escherichia coli,both genes mediated the conversion of beta-carotene to canthaxanthin.However in a zeaxanthin-producing E.coli,only the gene product of crtWJ48 introduced 4-keto groups into the 3,3'-dihydroxy carotenoid zeaxanthin yielding astaxanthin.The gene product of crtW38 was unable to catalyze this reaction.Both ketolases differ in their interaction with a hydroxylase in the biosynthetic pathway from beta-carotene to astaxanthin.