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 baculovirusgenerated 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 apocarotenoid 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.

Enzymatic Formation of β-Citraurin from β-Cryptoxanthin and Zeaxanthin by Carotenoid Cleavage Dioxygenase4 in the Flavedo of Citrus Fruit

“…In contrast to CCD1, CCD7, and CCD8, where the introns were conserved, in CCD4 the intron-exon structure was highly dynamic (Mein et al, 2011). In this study, no intron was observed in CitCCD4 in Yamashitabeni-wase or Miyagawa-wase (Supplemental Fig.…”

“…1). As carotenoids contain a series of conjugated double bonds in the central chain, they can be oxidatively cleaved in a site-specific manner (Mein et al, 2011). The oxidative cleavage of carotenoids not only regulates their accumulation but also produces a range of apocarotenoids (Walter et al, 2010).…”

BCDO2 acts as a carotenoid scavenger and gatekeeper for the mitochondrial apoptotic pathway

“…BCDO2 was first characterized as a BC and lycopene-metabolizing enzyme (Kiefer et al, 2001). Later, it was shown that this protein also catalyzes oxidative cleavage of carotenoids with 3-hydroxy-2973 RESEARCH ARTICLE BCDO2 in embryonic development ionone rings such as zeaxanthin and lutein (Mein et al, 2011;Amengual et al, 2011). We have demonstrated here that BCDO2 even cleaves canthaxanthin with 4-oxo-substituted ring sites.…”

Two Carotenoid Oxygenases Contribute to Mammalian Provitamin A Metabolism

“…Our results showed that BCO2 preferentially removed the 3-OH-␤-ionone ring site from this carotenoid. This preference for hydroxylated ring sites of carotenoids also has been reported for BCO2 from ferrets (30). Moreover, structural analyses and enzymatic properties of carotenoid oxygenases indicate that these enzymes specifically interact with one ionone ring side of their carotenoid substrates (51)(52)(53).…”