Comparative Analysis of β-Carotene Hydroxylase Genes for Astaxanthin Biosynthesis

• Published in: Journal of natural products (Washington, D.C.) Vol. 75; no. 6; pp. 1117 - 1124
• Main Authors: Scaife, Mark A, Ma, Cynthia A, Ninlayarn, Thanyanun, Wright, Phillip C, Armenta, Roberto E
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society and American Society of Pharmacognosy 22.06.2012
• Subjects: Archaea; Chromatography, High Pressure Liquid; Cyanobacteria; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - genetics; Escherichia coli - metabolism; Humans; Mixed Function Oxygenases - biosynthesis; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Molecular Structure; Xanthophylls - biosynthesis; Xanthophylls - chemistry; Xanthophylls - genetics; Xanthophylls - metabolism; Zeaxanthins
• ISSN: 0163-3864; 1520-6025
• DOI: 10.1021/np300136t

Astaxanthin (3,3′-dihydroxy-4,4′-diketo-β-carotene) (1) is a carotenoid of significant commercial value due to its superior antioxidant potential, application as a component of animal feeds, and ongoing research that links its application to the treatment and prevention of human pathologies. The high commercial cost of 1 is also based upon its complex synthesis. Chemical synthesis has been demonstrated, but produces a mixture of stereoisomers with limited applications. Production from biological sources is limited to natural producers with complex culture requirements. The biosynthetic pathway for 1 is well studied; however, questions remain that prevent optimized production in heterologous systems. Presented is a direct comparison of 12 β-carotene (2) hydroxylases derived from archaea, bacteria, cyanobacteria, and plants. Expression in Escherichia coli enables a comparison of catalytic activity with respect to zeaxanthin (3) and 1 biosynthesis. The most suitable β-carotene hydroxylases were subsequently expressed from an efficient dual expression vector, enabling 1 biosynthesis at levels up to 84% of total carotenoids. This supports efficient 1 biosynthesis by balanced expression of β-carotene ketolase and β-carotene hydroxylase genes. Moreover, our work suggests that the most efficient route for astaxanthin biosynthesis proceeds by hydroxylation of β-carotene to zeaxanthin, followed by ketolation.