Cloning and characterization of a novel ß-carotene hydroxylase gene from Lycium barbarum and its expression in Escherichia coli.

ABSTRACT

Lycium barbarum contains high levels of zeaxanthin, which is produced by the conversion of ß-carotene into zeaxanthin. ß-Carotene hydroxylase catalyzes this reaction. We cloned a cDNA (chyb) encoding ß-carotene hydroxylase (Chyb) from the L. barbarum leaf. A 939-bp full-length cDNA sequence was determined with 3'-rapid amplification of cDNA end assay encoding a deduced Chyb protein (34.8 kDa) with a theoretical isoelectric point of 8.36. A bioinformatics analysis showed that the L. barbarum Chyb was located in the chloroplast. Further, to investigate the catalytic activity of the L. barbarum Chyb, a complementation analysis was conducted in Escherichia coli. The results strongly demonstrated that Chyb can catalyze ß-carotene to produce zeaxanthin. Thus, this study suggests that L. barbarum ß-carotene hydroxylase could be a means of zeaxanthin production by genetic manipulation in E. coli.