Lipid components of the seagrasses Posidonia australis and Heterozostera tasmanica as indicators of carbon source

The component hydrocarbons, sterols, alcohols, monocarboxylic, α, ω-dicarboxylic and ω-hydroxy acids of the seagrasses Posidonia australis and Heterozostera tasmanica and a sample of P. australis detritus are reported. The fresh leaves of P. australis and P. australis detritus are characterized by a distinctive distribution of solvent-extractable long-chain monocarboxylic, α, ω-dicarboxylic and ω-hydroxy acids. This distinctive pattern should enable these lipid components along with other distinctive components to be used as chemical markers of the seagrass P. australis. H. tasmanica is characterized by (1) higher relative concentrations of 16:2ω6 and 16:3ω3 than P. australis, (2) the absence of the distinctive distribution pattern of long-chain monocarboxylic and ω-hydroxy acids observed for P. australis, (3) the absence of α, ω-diacids and (4) a lower absolute concentration of ω-hydroxy acids than P. australis.     

Lipids of the tropical seagrass Thallassia hemprichii

The component sterols, alcohols, hydrocarbons, monocarboxylic, α,ω-dicarboxylic and α- and ω-hydroxy acids from the leaves and roots of the tropical seagrass Thallassia hemprichii are reported. The leaves contained significant concentrations of cholest-5-en-3β-ol, a sterol not normally detected in either higher plants or seagrasses. The lower abundance of polyunsaturated fatty acids found in both the leaves and roots compared to other seagrass species may be a result of the warmer waters from which this species was collected. Solvent-extractable, long-chain (> C₂₂)α,ω-diacids, α- and ω-hydroxy and monocarboxylic acids were also isolated from the leaves. The distribution pattern of these lipids should enable these components along with other distinctive components to be used as chemical markers for this seagrass.     

A practical route to long-chain non-natural α,ω-diamino acids

An efficient method for the synthesis of long-chain α,ω-diamino acids, starting from natural α-amino acids, has been developed. The long-chain skeleton has been generated through condensation between a protected aldehyde, derived from l-aspartic acid, and an ylide obtained from an ω-hydroxy-alkyl phosphonium salt. After conversion of the ω-hydroxy group into an amine, catalytic hydrogenation produced the N,N′-protected α,ω-diamino acid. The present route to α,ω-diamino acids allows the modulation of the chain length depending on the length of the ylide used for the Wittig olefination reaction.     

Construction of an engineered biocatalyst system for the production of medium-chain α,ω-dicarboxylic acids from medium-chain ω-hydroxycarboxylic acids

Medium-chain α,ω-dicarboxylic acids produced from renewable long-chain fatty acids are valuable as precursors in the chemical industry. However, they are difficult to produce biologically at high concentrations. Although improved biocatalyst systems consisting of engineering of Baeyer–Villiger monooxygenases are used in the production of ω-hydroxycarboxylic acids from long-chain fatty acids, the engineering of biocatalysts involved in the production of α,ω-dicarboxylic acids from ω-hydroxycarboxylic acids has been rarely attempted. Here, we used highly active bacterial enzymes, Micrococcus luteus alcohol dehydrogenase and Archangium violaceum aldehyde dehydrogenase, for the efficient production of α,ω-dicarboxylic acids from ω-hydroxycarboxylic acids and constructed a biocatalyst with cofactor regeneration system by introducing NAD(P)H flavin oxidoreductase as the NAD(P)H oxidase. The inhibition of the biocatalyst by hydrophobic substrates was attenuated by engineering a biocatalyst system with an adsorbent resin, which allowed us to obtain 196 mM decanedioic, 145 mM undecanedioic, and 114 mM dodecanedioic acid from 200 mM of C10, C11, and C12 hydroxyl saturated carboxylic acids, respectively, and 141 mM undecanedioic acid from 150 mM C11 unsaturated carboxylic acids, with molar conversions of 98%, 97%, 95%, and 94%, respectively. The concentration of undecanedioic acid obtained was approximately 40-fold higher than that in the previously highest results. Our results from this study can be applied for the industrial production of medium-chain α,ω-dicarboxylic acids from renewable long-chain fatty acids.     

The biosynthesis of cutin and suberin as an alternative source of enzymes for the production of bio-based chemicals and materials

Oxygenated fatty acids such as ricinoleic acid and vernolic acid can serve in the industry as synthons for the synthesis of a wide range of chemicals and polymers traditionally produced by chemical conversion of petroleum derivatives. Oxygenated fatty acids can also be useful to synthesize specialty chemicals such as cosmetics and aromas. There is thus a strong interest in producing these fatty acids in seed oils (triacylglycerols) of crop species. In the last 15 years or so, much effort has been devoted to isolate key genes encoding proteins involved in the synthesis of oxygenated fatty acids and to express them in the seeds of the model plant Arabidopsis thaliana or crop species. An often overlooked but rich source of enzymes catalyzing the synthesis of oxygenated fatty acids and their esterification to glycerol is the biosynthetic pathways of the plant lipid polyesters cutin and suberin. These protective polymers found in specific tissues of all higher plants are composed of a wide variety of oxygenated fatty acids, many of which have not been reported in seed oils (e.g. saturated ω-hydroxy fatty acids and α,ω-diacids). The purpose of this mini-review is to give an overview of the recent advances in the biosynthesis of cutin and suberin and discuss their potential utility in producing specific oxygenated fatty acids for specialty chemicals. Special emphasis is given to the role played by specific acyltransferases and P450 fatty acid oxidases. The use of plant surfaces as possible sinks for the accumulation of high value-added lipids is also highlighted.     

The composition of suberin from the corks of Quercus suber L. and Betula pendula roth

The suberin constituents of Quercus suber and Betula pendula have been isolated after alkaline hydrolysis of the corks and over 80% by weight identified using thin-layer chromatography, preparative thin-layer chromatography, gas-liquid chromatography and combined gas chromatography — mass spectrometry. Long-chain aliphatic acids ranging from C₁₆–C₂₆ comprise about 90% of both suberin fractions; monobasic, α,ω-dibasic, ω-hydroxymonobasic, dihydroxymonobasic, dihydroxydibasic and trihydroxymonobasic acid classes are present. The principal suberin acids of Q. suber are 18-hydroxyoctadecenoic (12%), 22-hydroxydocosanoic (25%), 9,10-dihydroxyoctadecane-1,18-dioic (15%) and 9,10,18-trihydroxyoctadecanoic (8%), and those of B. pendula 9,10,18-trihydroxyoctadecanoic (43%) and 22-hydroxydocosanoic (16%).     

Arabidopsis Deficient in Cutin Ferulate encodes a transferase required for feruloylation of ω-hydroxy fatty acids in cutin polyester

The cuticle is a complex aliphatic polymeric layer connected to the cell wall and covers surfaces of all aerial plant organs. The cuticle prevents nonstomatal water loss, regulates gas exchange, and acts as a barrier against pathogen infection. The cuticle is synthesized by epidermal cells and predominantly consists of an aliphatic polymer matrix (cutin) and intracuticular and epicuticular waxes. Cutin monomers are primarily C(16) and C(18) unsubstituted, ω-hydroxy, and α,ω-dicarboxylic fatty acids. Phenolics such as ferulate and p-coumarate esters also contribute to a minor extent to the cutin polymer. Here, we present the characterization of a novel acyl-coenzyme A (CoA)-dependent acyl-transferase that is encoded by a gene designated Deficient in Cutin Ferulate (DCF). The DCF protein is responsible for the feruloylation of ω-hydroxy fatty acids incorporated into the cutin polymer of aerial Arabidopsis (Arabidopsis thaliana) organs. The enzyme specifically transfers hydroxycinnamic acids using ω-hydroxy fatty acids as acyl acceptors and hydroxycinnamoyl-CoAs, preferentially feruloyl-CoA and sinapoyl-CoA, as acyl donors in vitro. Arabidopsis mutant lines carrying DCF loss-of-function alleles are devoid of rosette leaf cutin ferulate and exhibit a 50% reduction in ferulic acid content in stem insoluble residues. DCF is specifically expressed in the epidermis throughout all green Arabidopsis organs. The DCF protein localizes to the cytosol, suggesting that the feruloylation of cutin monomers takes place in the cytoplasm.     

Some variations in the composition of suberin from the cork layers of higher plants

The monomeric composition of the suberins from 16 species of higher plants was determined by chromatographic methods following depolymerization of the isolated extractive-free cork layers with sodium methoxide-methanol. 1-Alkanols (mainly C₁₈C₂₈), alkanoic (mainly C₁₆C₃₀), α,ω-alkanedioic (mainly C₁₆C24), ω-hydroxyalkanoic (mainly C₁₆C₂₁), dihydroxyhexadecanoic (mainly 10,16-dihydroxy- and 16-dihydroxyhexadecanoic), monohydroxyepoxyalkanoic (9,10-epoxy-18-hydroxyoctadecanoic), trihydroxyalkanoic (9,10, 18-trihydroxyoctadecanoic), epoxyalkanedioic (9,10-epoxyoctadecane-1,18-dioic) and dihydroxyalkanedioic (9,10-dihydroxyoctadecane-1 18-dioic) acids were detected in all species. The suberins differed from one another mainly in the relative proportions of these monomer classes and in the homologue content of their 1-alkanol, alkanoic, α,ω-alkanedioic and ω-hydroxyalkanoic acid fractions. C₁₈ epoxy and vic-diol monomers were major components (32–59%) of half of the suberins examined (Quercus robur, Q. ilex, Q. suber, Fagus sylvatica, Castanea sativa, Betula pendula, Acer griseum, Fraxinus excelsior) where as ω-hydroxyalkanoic and α,ω-alkanedioic acids predominated in those that contained smaller quantities of such polar C₁₈ monomers (Acer pseudoplatanus, Ribes nigrum, Euonymus alatus, Populus tremula, Solanum tuberosum, Sambucus nigra, Laburnum anagyroides, Cupressus leylandii). All species, however, contained substantial amounts (14–55 %) of ω-hydroxyalkanoic acids, the most common homologues being 18:1 (9) and 22: 0. The dominant α,ω-alkanedioic acid homologues were 16: 0 and 18: 1 (9) whereas 22: 0, 24: 0 and 26: 0, and 20: 0, 22: 0 and 24: 0 were usually the principal homologues in the 1-alkanol and alkanoic acid fractions, respectively. The most diagnostic feature of the suberins examined was the presence of monomers greater than C₁₈ in chain length; most of the C₁₆ and C₁₈ monomers identified in the suberins also occur in plant cutins emphasizing the close chemical similarity between the two anatomical groups of lipid biopolymer.     

Constituent acids of Pinus radiata stem cutin

Stem cutin from P. radiata seedlings grown under winter and summer environmental conditions comprised n-alkanoic, (C₁₀–C₂₆), α, ω-alkanedioic (C₁₄–C₂₂), ω-hydroxyalkanoic (C₁₂–C₂₄), hydroxy-α, ω-alkanedioic and polyhydroxyalkanoic acids. 9-Hydroxyheptadecane-1, 17-dioic, 9-hydroxyoctadecene-1, 18-dioic, 9-hydroxynonadecane-1, 19-dioic, and 10, 17-dihydroxyheptadecanoic acids are newly-identified constituents of gymnosperm cutin. Cutin grown under winter temperatures and photoperiod contained twice the amount of 9, 16-dihydroxyhexadecanoic acid than that in summer-grown cutin, suggesting that the winter-grown cutin was formed from a highly cross-linked polymer, and that summer-grown cutin contained more linear polyester portions in the polymer.     

The constituent cutin acids of cranbury cuticle

Purified cutin from cranberry (Vaccinium macrocarpon, var. Howes) skin was selectively degraded, and the cutin acids, as methyl esters, separated by TLC into seven classes including monobasic acids, dibasic acids, monohydroxy monobasic acids, monohydroxy epoxymonobasic acids, vic-dihydroxy dibasic acids, dihydroxy monobasic acids and trihydroxy monobasic acids. Of the 41 components identified in cranberry cutin by GLC and MS analysis, 18-hydroxyoctadec-cis-9-enoic acid (9·4%), 18-hydroxy-cis-9,10-epoxyoctadecanoic acid (7·5%), 10,16-dihydroxyhexadecanoic acid (16·7%) and threo-9,10,18-trihydroxyoctadecanoic acid (43·7%) were shown to be the major constituents.     

Long-chain polyenoics and the essential dietary fatty acid requirement of the waxmoth, Galleria mellonella

The essential fatty acid requirement for normal pupal-adult ecdysis in Galleria mellonella was studied using non-axenic casein-based semisynthetic diets with or without various 99% pure fatty acids. The abilities of linoleic and linolenic acids to alleviate faulty adult emergence differed markedly, linolenic acid being 10-fold more potent than linoleic acid. One other ω6 polyunsaturated fatty acid, C20:2ω6, resembled its analogue, linoleic acid (18:2ω6), in efficacy at high dosage, but three others, C18:3ω6, C20: ω6 and C20:4ω6 (arachidonic acid), were without effect. Of five ω3 polyunsatures tested, C22:3ω3 and C20:3ω3 were as effective as linolenic acid (C18:3ω3), their shorter-chained analogue. Docosahexaenoic acid (C22:6ω3) was totally ineffective, but eicosapentaenoic acid (C20:5ω3), though supporting no perfect emergences, produced some active adults having wing malformations only, and was therefore considered partially active. It is suggested that a C18 polyunsaturate is physiologically required by G. mellonella and can be derived from various dietary longer-chained analogues by simple carbon chain shortening so long as there are no additional double bonds carboxylwards of an active di- or trienoic sequence. The partial activity of C20:5ω3 suggests there may additionally be a physiological requirement for this or a related long-chain polyunsaturate. The possibility of multiple essential fatty acid requirements in Lepidoptera in general is discussed.     

The composition of the cutin of the caryopses and leaves ofTriticum aestivum L.

The outer layers (bran) of white wheat (Triticum aestivum L. cv. Jubilar) caryopses contain several layers of lipophilic materials. It was the objective of the present work to establish the nature, composition and amounts of the lipid polymers of wheat bran and to compare it with leaf cutin. Prior to analysis, the bran was isolated and divided into two fractions: (i) the inner bran containing the remnants of the nucellus, the seed coat and the inner layers of the pericarp, and (ii) the outer bran consisting of the peripheral layers of the pericarp. Following depolymerization, a total number of 14 long-chain monobasic, dibasic, ω-hydroxymonobasic, α-hydroxymonobasic, dihydroxymonobasic, trihydroxymonobasic and epoxyhydroxymonobasic alkanoic acids have been identified as constituents of bran lipid polymeres. The most abundant single constituent was 9,10-epoxy-18-hydroxyoctadecanoic acid. The qualitative and quantitative compositions of depolymerisates from the inner and outer bran fractions were similar except for the absence of 9,10,18-trihydroxyoctadecanoic acid and of long-chain (C₂₂−C₂₆ ω-hydroxyalkanoic acids in the outer bran. The composition of bran depolymerisates closely resembled the constitution of the BF₃/CH₃OH susceptible fraction of wheat leaf cutin. Only less than 2% of the total amount of monomers released from inner bran were indicative for the presence of suberin. The total cutin content of wheat bran amounted to 4.2 g per kg of dry caryopses. Most of it (96.6%) was contributed by the cuticles of the seed coat and the nucellus while the cuticle of the pericarp made up only 3.4%.     

Intracuticular lipids of spinach leaves

The cuticular wax and cutin components of the cuticular membranes isolated from the leaves of two spinach cultivars have been determined. The membranes contain about 0·007 mg/cm² of cuticular wax which comprises monobasic acids (C₁₆–C₃₈) with hexadecanoic as the major component. The amounts of cutin are comparable with those of cuticular wax and the monomeric constituents are predominantly C₁₈ epoxy compounds. The most abundant monomer is 9,10-epoxy-18-hydroxyoctadecanoic acid (up to 63%) together with substantial amounts of 9,10,18-trihydroxyoctadecanoic acid (up to 22%). Also present are 9,10-epoxyoctadecane-1,18-dioic acid (6–7%) dihydroxyhexadecanoic acid (3–4%) and ω-hydroxymonobasic and fatty acid fractions. The tentative identification of two minor components, 18-hydroxyoxooctadecanoic and 9,10-epoxy-12,18-dihydroxyoctadecanoic acids, is also made. Although spinach membranes have a delicate structure their cutin composition is essentially similar to that of much more substantial membranes.     

Biocatalytic,one-pot diterminal oxidation and esterification of n-alkanes for production of α,ω-diol and α,ω-dicarboxylic acid esters

Direct and selective terminal oxidation of medium-chain n-alkanes is a major challenge in chemistry. Efforts to achieve this have so far resulted in low specificity and overoxidized products. Biocatalytic oxidation of medium-chain n-alkanes – with for example the alkane monooxygenase AlkB from P. putida GPo1- on the other hand is highly selective. However, it also results in overoxidation. Moreover, diterminal oxidation of medium-chain n-alkanes is inefficient. Hence, α,ω-bifunctional monomers are mostly produced from olefins using energy intensive, multi-step processes.By combining biocatalytic oxidation with esterification we drastically increased diterminal oxidation upto 92 mol% and reduced overoxidation to 3% for n-hexane. This methodology allowed us to convert medium-chain n-alkanes into α,ω-diacetoxyalkanes and esterified α,ω-dicarboxylic acids. We achieved this in a one-pot reaction with resting-cell suspensions of genetically engineered Escherichia coli.The combination of terminal oxidation and esterification constitutes a versatile toolbox to produce α,ω-bifunctional monomers from n-alkanes.     

短小芽孢杆菌肉碱转运系统opuC基因的克隆与序列分析

以前期获得的ω-1-羟基脂肪酸高产突变菌株短小芽孢杆菌(Bacillus pumilus)M-F641的总DNA为模板,利用Primer Premier 5.0软件设计4对引物,对决定长链脂肪酸无效降解途径中肉碱转运的OpuC转运系统的基因进行克隆,成功获得了opuCA、opuCB、opuCC和opuCD的基因序列,并利用MEGA 3.1、DNAStar等软件进行序列分析.研究内容将为进一步利用短小芽孢杆菌长链脂肪酸高效转化生产ω-1-羟基脂肪酸菌株奠定基础.     

Determination of hydroxylated fatty acids from the biopolymer of tomato cutin and their fate during incubation in soil

Introduction – The plant cuticle is a thin, predominantly lipid layer that covers all primary aerial surfaces of vascular plants. The monomeric building blocks of the cutin biopolymer are mainly ω‐hydroxy fatty acids. Objective – Analysis of ω‐hydroxy fatty acids from cutin isolated from tomato fruits at different stages of decomposition in soil. Different derivatives and mass spectrometric techniques were used for peak identification and evaluation. Methodology – Preparation of purified cutin involving dewaxing and HCl treatment. Incubation of purified cutin for 20 months in soil. Pentafluorobenzoyl derivatives were used for GC/MS operated in the electron capture negative ion (ECNI) mode and trimethylsilyl ethers for GC/MS operated in the electron ionisation (EI) mode for analysis of ω‐hydroxy fatty acids. Results – Six ω‐hydroxy fatty acids were detected in the purified cutin, three of which were identified as degradation products of 9,16‐dihydroxyhexadecanoic acid as a consequence of the HCl treatment involved in the purification step. Incubation of the isolated cutin in soil was accompanied with decrease in concentration of all hydroxyl fatty acids. Conclusion – We produced evidence that the HCl treatment only affected free hydroxyl groups and thus could be used for proportioning free and bound OH‐groups on cutin fatty acids. The method enabled a direct quantification of the ω‐hydroxy fatty acids throughout the incubation phase. Copyright © 2010 John Wiley & Sons, Ltd.     

Methyl-end desaturases with ∆12 and ω3 regioselectivities enable the de novo PUFA biosynthesis in the cephalopod Octopus vulgaris

The interest in understanding the capacity of aquatic invertebrates to biosynthesise omega-3 (ω3) long-chain (≥C₂₀) polyunsaturated fatty acids (LC-PUFA) has increased in recent years. Using the common octopus Octopus vulgaris as a model species, we previously characterised a ∆5 desaturase and two elongases (i.e. Elovl2/5 and Elovl4) involved in the biosynthesis of LC-PUFA in molluscs. The aim of this study was to characterise both molecularly and functionally, two methyl-end (or ωx) desaturases that have been long regarded to be absent in most animals. O. vulgaris possess two ωx desaturase genes encoding enzymes with ∆12 and ω3 regioselectivities enabling the de novo biosynthesis of the C₁₈ PUFA 18:2ω6 (LA, linoleic acid) and 18:3ω3 (ALA, α-linolenic acid), generally regarded as dietary essential for animals. The O. vulgaris ∆12 desaturase (“ωx2”) mediates the conversion of 18:1ω9 (oleic acid) into LA, and subsequently, the ω3 desaturase (“ωx1”) catalyses the ∆15 desaturation from LA to ALA. Additionally, the O. vulgaris ω3 desaturase has ∆17 capacity towards a variety of C₂₀ ω6 PUFA that are converted to their ω3 PUFA products. Particularly relevant was the affinity of the ω3 desaturase towards 20:4ω6 (ARA, arachidonic acid) to produce 20:5ω3 (EPA, eicosapentaenoic acid), as supported by yeast heterologous expression, and enzymatic activity exhibited in vivo when paralarvae were incubated in the presence of [1-¹⁴C]20:4ω6. These results confirmed that several routes enabling EPA biosynthesis are operative in O. vulgaris whereas ARA and docosahexaenoic acid (DHA, 22:6ω3) should be considered essential fatty acids since endogenous production appears to be limited.     

Chemical synthesis and biological evaluation of ω-hydroxy polyunsaturated fatty acids

ω-Hydroxy polyunsaturated fatty acids (PUFAs), natural metabolites from arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were prepared via convergent synthesis approach using two key steps: Cu-mediated CC bond formation to construct methylene skipped poly-ynes and a partial alkyne hydrogenation where the presence of excess 2-methyl-2-butene as an additive that is proven to be critical for the success of partial reduction of the poly-ynes to the corresponding cis-alkenes without over-hydrogenation. The potential biological function of ω-hydroxy PUFAs in pain was evaluated in naive rats. Following intraplantar injection, 20-hydroxyeicosatetraenoic acid (20-HETE, ω-hydroxy ARA) generated an acute decrease in paw withdrawal thresholds in a mechanical nociceptive assay indicating pain, but no change was observed from rats which received either 20-hydroxyeicosapentaenoic acid (20-HEPE, ω-hydroxy EPA) or 22-hydroxydocosahexaenoic acid (22-HDoHE, ω-hydroxy DHA). We also found that both 20-HEPE and 22-HDoHE are more potent than 20-HETE to activate murine transient receptor potential vanilloid receptor1 (mTRPV1).     

Fatty acid ω-hydroxylases from <Emphasis Type="Italic">Solanum tuberosum</Emphasis>

Key message

Potato StCYP86A33 complements the Arabidopsis AtCYP86A1 mutant, horst - 1.

Abstract

Suberin is a cell-wall polymer that comprises both phenolic and aliphatic components found in specialized plant cells. Aliphatic suberin is characterized by bi-functional fatty acids, typically ω-hydroxy fatty acids and α,ω-dioic acids, which are linked via glycerol to form a three-dimensional polymer network. In potato (Solanum tuberosum L.), over 65 % of aliphatics are either ω-hydroxy fatty acids or α,ω-dioic acids. Since the biosynthesis of α,ω-dioic acids proceeds sequentially through ω-hydroxy fatty acids, the formation of ω-hydroxy fatty acids represents a significant metabolic commitment during suberin deposition. Four different plant cytochrome P450 subfamilies catalyze ω-hydroxylation, namely, 86A, 86B, 94A, and 704B; though to date, only a few members have been functionally characterized. In potato, CYP86A33 has been identified and implicated in suberin biosynthesis through reverse genetics (RNAi); however, attempts to express the CYP86A33 protein and characterize its catalytic function have been unsuccessful. Herein, we describe eight fatty acid ω-hydroxylase genes (three CYP86As, one CYP86B, three CYP94As, and a CYP704B) from potato and demonstrate their tissue expression. We also complement the Arabidopsis cyp86A1 mutant horst-1 using StCYP86A33 under the control of the Arabidopsis AtCYP86A1 promoter. Furthermore, we provide preliminary analysis of the StCYP86A33 promoter using a hairy root transformation system to monitor pStCYP86A33::GUS expression constructs. These data confirm the functional role of StCYP86A33 as a fatty acid ω-hydroxylase, and demonstrate the utility of hairy roots in the study of root-specific genes.

     

ω-Hydroxylation of α-tocopheryl quinone reveals a dual function for cytochrome P450-4F2 in vitamin E metabolism

α-Tocopherol (α-TOH) is the primary lipophilic radical trapping antioxidant in human tissues. Oxidative catabolism of α-tocopherol (αTOH) is initiated by ω-hydroxylation of the terminal carbon (C-13) of the isoprenoid sidechain followed by oxidative transformations that sequentially truncate the chain to yield the 2,5,7,8-tetramethyl(3′carboxyethyl)-6-hydroxychroman (α-CEHC). After conjugation to glucuronic acid, 3′-carboxyethyl-6-hydroxychroman glucuronide is excreted in urine. We report here that the same enzyme that accomplishes this task, the cytochrome P450 monooxygenase CYP-4F2, can also ω-hydroxylate the terminal carbon of α-tocopheryl quinone. A standard sample of ω-OH-α-tocopheryl quinone (ω-OH-α-TQ) was synthesized as a mixture of stereoisomers by allylic oxidation of α-tocotrienol using SeO₂ followed by double-bond reduction and oxidation to the quinone. After incubating human liver microsomes or insect cell microsomes expressing only recombinant human CYP-4F2, cytochrome b5, and NADPH P450 reductase with d₆-α-tocopheryl quinone (d₆-αTQ), we showed that the ω-hydroxylated (13-OH) d₆-α-TQ was produced. We further identified the production of the terminal carboxylic acid d₆-13-COOH-αTQ. The ramifications of this discovery to the understanding of tocopherol utilization and metabolism, including the quantitative importance of the αTQ-ω-hydroxylase pathway in humans, are discussed.