The dihydroxy xanthophylls lutein (β,var epsilon-carotene-3,3′-diol) and zeaxanthin (β,β-carotene-3,3′-diol) are well known for their critical roles in photosystem structure and adaptation of plants to high light stress. As a group, carotenoid hydroxylases catalyze the formation of lutein and zeaxanthin from their corresponding cyclic carotene precursors. Carotenoid β-ring hydroxylases (β-hydroxylases) have been isolated and characterized from various organisms and have invariably been shown to be non-heme di-iron monooxygenases. The presence of an var epsilon-ring specific hydroxylase (var epsilon-hydroxylase) was genetically demonstrated by isolation of mutants at the LUT1 locus in Arabidopsis. This review focuses on progress in understanding the molecular and biochemical nature of the var epsilon-hydroxylase and the in vivo overlapping functions of the various carotenoid β- and var epsilon-hydroxylases in Arabidopsis.
Archives of Biochemistry and Biophysics (2004) 430 (1) 22-29 [doi:10.1016/j.abb.2004.02.003]