title: Enzymatic formation of apo-carotenoids from the xanthophyll carotenoids lutein, zeaxanthin and β-cryptoxanthin by ferret carotene-9',10'-monooxygenase.
abstract: Xanthophyll carotenoids, such as lutein, zeaxanthin and β-cryptoxanthin, may provide potential health benefits against chronic and degenerative diseases. Investigating pathways of xanthophyll metabolism are important to understanding their biological functions. Carotene-15,15'-monooxygenase (CMO1) has been shown to be involved in vitamin A formation, while recent studies suggest that carotene-9',10'-monooxygenase (CMO2) may have a broader substrate specificity than previously recognized. In this in vitro study, we investigated baculovirus-generated recombinant ferret CMO2 cleavage activity towards the carotenoid substrates zeaxanthin, lutein and β-cryptoxanthin. Utilizing HPLC, LC-MS and GC-MS, we identified both volatile and non-volatile apo-carotenoid products including 3-OH-β-ionone, 3-OH-α-ionone, β-ionone, 3-OH-α-apo-10'-carotenal, 3-OH-β-apo-10'-carotenal, and β-apo-10'-carotenal, indicating cleavage at both the 9,10 and 9',10' carbon-carbon double bond. Enzyme kinetic analysis indicated the xanthophylls zeaxanthin and lutein are preferentially cleaved over β-cryptoxanthin, indicating a key role of CMO2 in non-provitamin A carotenoid metabolism. Furthermore, incubation of 3-OH-β-apo-10'-carotenal with CMO2 lysate resulted in the formation of 3-OH-β-ionone. In the presence of NAD(+), in vitro incubation of 3-OH-β-apo-10'-carotenal with ferret hepatic homogenates formed 3-OH-β-apo-10'-carotenoic acid. Since apo-carotenoids serve as important signaling molecules in a variety of biological processes, enzymatic cleavage of xanthophylls by mammalian CMO2 represents a new avenue of research regarding vertebrate carotenoid metabolism and biological function.
authors.affiliation: Nutrition and Cancer Biology Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Mein
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Dolnikowski
authors.forename: Hansgeorg
authors.initials: H
authors.lastname: Ernst
authors.forename: Robert M
authors.initials: RM
authors.lastname: Russell
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Wang
mesh_terms: D000818:Animals; D002338:Carotenoids / Q000096:biosynthesis* / Q000737:chemistry; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D065366:Cryptoxanthins; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D005289:Ferrets / Q000235:genetics / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D014975:Lutein / Q000378:metabolism; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera; D013379:Substrate Specificity; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D065366:Cryptoxanthins; D011994:Recombinant Proteins; D024341:Xanthophylls; D065146:Zeaxanthins; D002338:Carotenoids; D044943:Fatty Acid Desaturases; D014975:Lutein