Enzymatic formation of apo-carotenoids from the xanthophyll carotenoids lutein, zeaxanthin and ?-cryptoxanthin by ferret carotene-9',10'-monooxygenase.

ABSTRACT: Xanthophyll carotenoids, such as lutein, zeaxanthin and ?-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 ?-cryptoxanthin. Utilizing HPLC, LC-MS and GC-MS, we identified both volatile and non-volatile apo-carotenoid products including 3-OH-?-ionone, 3-OH-?-ionone, ?-ionone, 3-OH-?-apo-10'-carotenal, 3-OH-?-apo-10'-carotenal, and ?-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 ?-cryptoxanthin, indicating a key role of CMO2 in non-provitamin A carotenoid metabolism. Furthermore, incubation of 3-OH-?-apo-10'-carotenal with CMO2 lysate resulted in the formation of 3-OH-?-ionone. In the presence of NAD(+), in vitro incubation of 3-OH-?-apo-10'-carotenal with ferret hepatic homogenates formed 3-OH-?-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.

SUBMITTER: Mein JR 

PROVIDER: S-EPMC3026080 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature