Occurrence of diaminopimelic epimerase in maize

Extracts of maize leaves catalyzed the interconversion of meso-diaminopimelic acid its L-isomer. Three observations support the existence of this epimerase activity: (i) detection of the reversible interconversion of L-diaminopimelic acid and meso-diaminopimelic acid by paper chromatography after incubation of either isomer with extract; (ii) formation of [¹⁴C]CO₂ from L-[¹⁴C]diaminopimelic acid in an incubation mix containing meso-diaminopimelic acid decarboxylase; and (iii) inhibition of [¹⁴C]CO₂ evolution from L-diaminopimelic acid by unlabeled meso-diaminopimelic acid. The demonstration of the diaminopimelic acid epimerase lends support to the occurrence in plants of the complete diaminopimelic acid pathway for biosynthesis of lysine as it occurs in Escherichia coli and most bacteria.     

Differential modes of crosslinking establish spatially distinct regions of peptidoglycan in Caulobacter crescentus

The diversity of cell shapes across the bacterial kingdom reflects evolutionary pressures that have produced physiologically important morphologies. While efforts have been made to understand the regulation of some prototypical cell morphologies such as that of rod‐shaped Escherichia coli, little is known about most cell shapes. For Caulobacter crescentus, polar stalk synthesis is tied to its dimorphic life cycle, and stalk elongation is regulated by phosphate availability. Based on the previous observation that C. crescentus stalks are lysozyme‐resistant, we compared the composition of the peptidoglycan cell wall of stalks and cell bodies and identified key differences in peptidoglycan crosslinking. Cell body peptidoglycan contained primarily DD‐crosslinks between meso‐diaminopimelic acid and D‐alanine residues, whereas stalk peptidoglycan had more LD‐transpeptidation (meso‐diaminopimelic acid‐meso‐diaminopimelic acid), mediated by LdtD. We determined that ldtD is dispensable for stalk elongation; rather, stalk LD‐transpeptidation reflects an aging process associated with low peptidoglycan turnover in the stalk. We also found that lysozyme resistance is a structural consequence of LD‐crosslinking. Despite no obvious selection pressure for LD‐crosslinking or lysozyme resistance in C. crescentus, the correlation between these two properties was maintained in other organisms, suggesting that DAP‐DAP crosslinking may be a general mechanism for regulating bacterial sensitivity to lysozyme.     

Second bioluminescence‐activating component in the luminous fungus Mycena chlorophos

Mycena chlorophos is an oxygen‐dependent bioluminescent fungus. The mechanisms underlying its light emission are unknown. A component that increased the bioluminescence intensity of the immature living gills of M. chlorophos was isolated from mature M. chlorophos gills and chemically characterized. The bioluminescence‐activating component was found to be trans‐3,4‐dihydroxycinnamic acid and its bioluminescence activation was highly structure‐specific. ¹³C‐ and ¹⁸O‐labelling studies using the immature living gills showed that trans‐3,4‐dihydroxycinnamic acid was synthesized from trans‐4‐hydroxycinnamic acid in the gills by hydroxylation with molecular oxygen as well as by the general metabolism, and trans‐3,4‐dihydroxycinnamic acid did not produce hispidin (detection‐limit concentration: 10 pmol/1 g wet gill). Addition of 0.01 mM hispidin to the immature living gills generated no bioluminescence activation. These results suggested that the prompt bioluminescence activation resulting from addition of trans‐3,4‐dihydroxycinnamic acid could not be attributed to the generation of hispidin. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and Quantitative Analysis of Diastereomeric Linked Ester Conjugates With Remote Stereocenters Using High‐Field NMR and Chiral HPLC

A stereochemically safe high‐yielding procedure for linking unprotected as well as protected hydroxycarboxylic acids to chiral secondary alcohols via glycolic acid linker is proposed. L‐menthol has been linked with both enantiomers of mandelic, malic, and methoxyphenylacetic acid using bromo‐ or iodoacetyl group as a precursor of the glycolic acid linker. High‐field nuclear magnetic resonance (NMR) and chiral high‐performance liquid chromatography (HPLC) determination of high diastereomeric ratio (dr) (>99%) of the products bearing remote stereocenters was explored. Chiral HPLC allowed quantitation of the diastereomers up to dr 99.9/0.1. High‐field NMR quantitation of the diastereomeric and parent alcoholic impurities in esters was demonstrated at the molar 0.3% and 0.03% levels, respectively. These analyses were done via comparison of integral intensities from major component ¹³C satellites in ¹H or even in ¹³C spectra to the ¹H or ¹³C signals of impurities. Despite lower sensitivity, the last option generally has much better selectivity. In this way the dynamic resolution is brought down by two orders. Chirality 25:793–798, 2013. © 2013 Wiley Periodicals, Inc.     

Efficient Preparation of (R)‐2‐chloromandelic Acid Via a Recycle Process of Resolution

Efficient preparation of (R)‐2‐chloromandelic acid (R)-1 based on a recycle process of resolution is described. In the process, the desired (R)-1 was obtained by coordination‐mediated resolution with D‐O,O'‐di‐(p‐toluoyl)‐tartaric acid in the presence of Ca²⁺. Meanwhile, the undesired (S)-1 could be racemized in the presence of sodium hydroxide and the product was suitable for further resolution. A carbanion mechanism for the racemization of (S)-1 is proposed. Chirality 27:281–285, 2015. © 2015 Wiley Periodicals, Inc.     

The Myo‐inositol pathway does not contribute to ascorbic acid synthesis

• Ascorbic acid (AsA) biosynthesis in plants predominantly occurs via a pathway with d ‐mannose and l ‐galactose as intermediates. One alternative pathway for AsA synthesis, which is similar to the biosynthesis route in mammals, is controversially discussed for plants. Here, myo‐inositol is cleaved to glucuronic acid and then converted via l ‐gulonate to AsA. In contrast to animals, plants have an effective recycling pathway for glucuronic acid, being a competitor for the metabolic rate. Recycling involves a phosphorylation at C1 by the enzyme glucuronokinase.
• Two previously described T‐DNA insertion lines in the gene coding for glucuronokinase1 show wild type‐like expression levels of the mRNA in our experiments and do not accumulate glucuronic acid in labelling experiments disproving that these lines are true knockouts. As suitable T‐DNA insertion lines were not available, we generated frameshift mutations in the major expressed isoform glucuronokinase1 (At3g01640) to potentially redirect metabolites to AsA.
• However, radiotracer experiments with ³H‐myo‐inositol revealed that the mutants in glucuronokinase1 accumulate only glucuronic acid and incorporate less metabolite into cell wall polymers. AsA was not labelled, suggesting that Arabidopsis cannot efficiently use glucuronic acid for AsA biosynthesis.
• All four mutants in glucuronokinase as well as the wild type have the same level of AsA in leaves.

     

On‐Line Activity Screening for Radical Scavengers from Baccharis chilco

Baccharis plants have been used since ancient times in American traditional medicine. Baccharis chilco is a perennial shrub of temperate regions of South America that grows well in rainfall forests of Colombia. Neither chemical composition nor biological studies of this plant have ever been reported. Two caffeoylquinic acid (CQA) derivatives, 5‐O‐[(E)‐caffeoyl]quinic acid ( 1 ) and 3,5‐di‐O‐[(E)‐caffeoyl]quinic acid ( 3 ), and rosmarinic acid ( 2 ) have been isolated from B. chilco growing wild in Colombia, using the on‐line HPLC‐DAD‐DPPH radical‐scavenging detection technique as guidance. In the course of the purification work, L ‐chiro‐inositol ( 4 ) was also isolated. Structures of the four isolated compounds were determined by spectroscopic methods. Antioxidants 2 and 3 exhibited high antiradical activities evaluated by the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH^.) assay, although somewhat lower than that of the reference compound ascorbic acid. The on‐line HPLC‐DAD‐DPPH technique allowed a rapid pinpointing of antioxidants in the studied EtOH extract, and the facile guided isolation of the target molecules.     

Aerobic biodegradation of a mixture of sulfonated azo dyes by a bacterial consortium immobilized in a two‐stage sparged packed‐bed biofilm reactor

The biodegradation of the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid Red 88 (AR88), by a bacterial consortium isolated from water and soil samples obtained from sites receiving discharges from textile industries, was evaluated. For a better removal of azo dyes and their biodegradation byproducts, an aerobically operated two‐stage rectangular packed‐bed biofilm reactor (2S‐RPBR) was constructed. Because the consortium's metabolic activity is affected by oxygen, the effect of the interstitial air flow rate Q_GI on 2S‐RPBR's zonal values of the oxygen mass transfer coefficient k_La was estimated. In the operational conditions probed in the bioreactor, the k_La values varied from 3 to 60 h^?1, which roughly correspond to volumetric oxygen transfer rates, dc_L/dt, ranging from 20 to 375 mg O₂ L^?1h^?1. Complete biodegradation of azo dyes was attained at loading rates B_V,AZ up to 40 mg L^?1d^?1. At higher B_V,AZ values (80 mg L^?1 d^?1), dye decolorization and biodegradation of the intermediaries 4‐amino‐naphthalenesulphonic acid (4‐ANS) and 1‐amino‐2‐naphthol (1‐A2N) was almost complete. However, a diminution in COD and TOC removal efficiencies was observed in correspondence to the 4‐aminobenzenesulfonic acid (4‐ABS) accumulation in the bioreactor. Although the oxygen transport rate improved the azo dye mineralization, the results suggest that the removal efficiency of azo dyes was affected by biofilm detachment at relatively high Q_GI and B_V,AZ values. After 225 days of continuous operation of the 2S‐RFBR, eight bacterial strains were isolated from the biofilm attached to the porous support. The identified genera were: Arthrobacter, Variovorax, Agrococcus, Sphingomonas, Sphingopyxis, Methylobacterium, Mesorhizobium, and Microbacterium.     

Microbial production of conjugated γ‐linolenic acid from γ‐linolenic acid by Lactobacillus plantarum AKU 1009a

Aims: Optimal production conditions of conjugated γ‐linolenic acid (CGLA) from γ‐linolenic acid using washed cells of Lactobacillus plantarum AKU 1009a as catalysts were investigated. Methods and Results: Washed cells of Lact. plantarum AKU 1009a exhibiting a high level of CGLA productivity were obtained by cultivation in a nutrient medium supplemented with 0·03% (w/v) α‐linolenic acid as an inducer. Under the optimal reaction conditions with 13 mg ml^?1γ‐linolenic acid as a substrate in 5 ‐ml reaction volume, the washed cells [32% (wet cells, w/v) corresponding to 46 mg ml^?1 dry cells] as the catalysts produced 8·8 mg CGLA per millilitre reaction mixture (68% molar yield) in 27 h. The produced CGLA was a mixture of two isomers, i.e., cis‐6,cis‐9,trans‐11‐octadecatrienoic acid (CGLA1, 40% of total CGLA) and cis‐6,trans‐9,trans‐11‐octadecatrienoic acid (CGLA2, 60% of total CGLA), and accounted for 66% of total fatty acid obtained. The CGLA produced was obtained as free fatty acids adsorbed mostly on the surface of the cells of Lact. plantarum AKU1009a. Conclusion: The practical process of CGLA production from γ‐linolenic acid using washed cells of Lact. plantarum AKU 1009a was successfully established. Significance and Impact of the Study: We presented the first example of microbial production of CGLA. CGLA produced by the process is valuable for evaluating their physiological and nutritional effects, and chemical characteristics.     

A new ferulic acid ester, a new ellagic acid derivative, and other constituents from pachycentria formosana: effects on neutrophil pro-inflammatory responses

A new ferulic acid ester derivative, tetracosane‐1,24‐diyl di[(Z)‐ferulate] ( 1 ), and a new ellagic acid derivative, 3,4 : 3′,4′‐bis(O,O‐methylene)ellagic acid ( 2 ), have been isolated from leaves and twigs of Pachycentria formosana, together with eight known compounds. Their structures were determined by in‐depth spectroscopic and mass‐spectrometric analyses. Among the isolated compounds, oleanolic acid ( 6 ), ursolic acid acetate ( 7 ), and 3‐epibetulinic acid ( 9 ) exhibited potent inhibition (IC₅₀ values ≤21.8 μM ) of O₂^⋅− generation by human neutrophils in response to N‐formyl‐L ‐methionyl‐L ‐leucyl‐L ‐phenylalanine/cytochalasin B (fMLP/CB). In addition, oleanolic acid ( 6 ), 3‐O‐[(E)‐feruloyl]ursolic acid ( 8 ), 3‐epibetulinic acid ( 9 ), and lawsonic acid ( 10 ) also inhibited fMLP/CB‐induced elastase release with IC₅₀ values ≤18.6 μM .     

An Alternative Standard for Trolox‐Equivalent Antioxidant‐Capacity Estimation Based on Thiol Antioxidants. Comparative 2,2′‐Azinobis[3‐ethylbenzothiazoline‐6‐sulfonic Acid] Decolorization and Rotational Viscometry Study Regarding Hyaluronan Degradation

Comparison of the effectiveness of antioxidant activity of three thiol compounds, D ‐penicillamine, reduced L ‐glutathione, and 1,4‐dithioerythritol, expressed as a radical‐scavenging capacity based on the two independent methods, namely a decolorization 2,2′‐azinobis[3‐ethylbenzothiazoline‐6‐sulfonic acid] assay and a rotational viscometry, is reported. Particular concern was focused on the testing of potential free‐radical scavenging effects of thiols against hyaluronan degradation, induced by hydroxyl radicals. A promising, solvent‐independent, antioxidative function of 1,4‐dithioerythritol, comparable to that of a standard compound, Trolox^®, was confirmed by the 2,2′‐azinobis[3‐ethylbenzothiazoline‐6‐sulfonic acid] assay. The new potential antioxidant 1,4‐dithioerythritol exhibited very good solubility in a variety of solvents (e.g., H₂O, EtOH, and DMSO) and could be widely accepted and used as an effective antioxidant standard instead of a routinely used Trolox^® on 2,2′‐azinobis[3‐ethylbenzothiazoline‐6‐sulfonic acid] assay.     

Die Beurteilung des Einflusses qualitativer Prüffaktoren (Infektionstermine,Sorten) auf den Befall mit Hilfe der Kontingenztafelanalyse

Mycelial growth of some wood‐rotting fungi was studied on a solid modified medium MS (Murashige and Skoog, 1962) with indole‐3‐acetic acid at concentrations of 10^‐6 to 10^‐3 M. The IAA concentrations of 10^‐6 M and 10^‐5 M inhibited mycelial growth of the fungus Phaeolus schweinitzii, Laetiporus sulphureus and Pleurotus ostreatus while the same concentrations stimulated mycelial growth of the fungus Stereum rugosum. The IAA concentrations of 10^‐6 M stimulated mycelial growth in Piptoporus betulinus and temporarily stimulated mycelial growth in Heterobasidion annosum. The IAA concentration of 10^‐4 M appeared critical for wood‐rotting fungi. The IAA concentration of 10^‐3 M inhibited mycelial growth in all the fungi under study.     

Structure and functional characterization of a bile acid 7α dehydratase BaiE in secondary bile acid synthesis

Conversion of the primary bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) to the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA) is performed by a few species of intestinal bacteria in the genus Clostridium through a multistep biochemical pathway that removes a 7α‐hydroxyl group. The rate‐determining enzyme in this pathway is bile acid 7α‐dehydratase (baiE). In this study, crystal structures of apo‐BaiE and its putative product‐bound [3‐oxo‐Δ^4,6‐lithocholyl‐Coenzyme A (CoA)] complex are reported. BaiE is a trimer with a twisted α + β barrel fold with similarity to the Nuclear Transport Factor 2 (NTF2) superfamily. Tyr30, Asp35, and His83 form a catalytic triad that is conserved across this family. Site‐directed mutagenesis of BaiE from Clostridium scindens VPI 12708 confirm that these residues are essential for catalysis and also the importance of other conserved residues, Tyr54 and Arg146, which are involved in substrate binding and affect catalytic turnover. Steady‐state kinetic studies reveal that the BaiE homologs are able to turn over 3‐oxo‐Δ⁴‐bile acid and CoA‐conjugated 3‐oxo‐Δ⁴‐bile acid substrates with comparable efficiency questioning the role of CoA‐conjugation in the bile acid metabolism pathway. Proteins 2016; 84:316–331. © 2016 Wiley Periodicals, Inc.     

Conformations of peptides containing a chiral cyclic α, α‐disubstituted α‐amino acid within the sequence of Aib residues

A single chiral cyclic α,α‐disubstituted amino acid, (3S,4S)‐1‐amino‐(3,4‐dimethoxy)cyclopentanecarboxylic acid [(S,S)‐Ac₅c^dOM], was placed at the N‐terminal or C‐terminal positions of achiral α‐aminoisobutyric acid (Aib) peptide segments. The IR and ¹H NMR spectra indicated that the dominant conformations of two peptides Cbz‐[(S,S)‐Ac₅c^dOM]‐(Aib)₄‐OEt ( 1) and Cbz‐(Aib)₄‐[(S,S)‐Ac₅c^dOM]‐OMe (2) in solution were helical structures. X‐ray crystallographic analysis of 1 and 2 revealed that a left‐handed (M) 3₁₀‐helical structure was present in 1 and that a right‐handed (P) 3₁₀‐helical structure was present in 2 in their crystalline states. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Auxin and cytokinin relationships in 24 microalgal strains1

Endogenous auxins and cytokinins were quantitated in 24 axenic microalgal strains from the Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Charophyceae. These strains were in an exponential growth phase, being harvested on day 4. Acutodesmus acuminatus Mosonmagyaróvár Algal Culture Collection‐41 (MACC) produced the highest biomass and Chlorococcum ellipsoideum MACC‐712 the lowest biomass. The auxins, indole‐3‐acetic acid (IAA) and indole‐3‐acetamide (IAM) were present in all microalgal strains. No other auxin conjugates were detected. IAA and IAM concentrations varied greatly, ranging from 0.50 to 71.49 nmol IAA · g^?1 DW and 0.18 to 99.83 nmol IAM · g^?1 DW, respectively. In 19 strains, IAA occurred in higher concentrations than IAM. Nineteen cytokinins were identified in the microalgal strains. Total cytokinin concentrations varied, ranging from 0.29 nmol · g^?1 DW in Klebsormidium flaccidum MACC‐692 to 21.40 nmol · g^?1 DW in Stigeoclonium nanum MACC‐790. The general trend was that cis‐zeatin types were the predominant cytokinins; isopentenyladenine‐type cytokinins were present in moderate concentrations, while low levels of trans‐zeatin‐type and very low levels of dihydrozeatin‐type cytokinins were detected. Ribotides were generally the main cytokinin conjugate forms present with the cytokinin free bases and ribosides present in similar but moderate levels. The levels of O‐glucosides were low. Only one N‐glucoside was detected, being present in nine strains in very low concentrations. In 15 strains, the auxin content was 2‐ to 4‐fold higher than the cytokinin content.     

Improved anticancer potency by head‐to‐tail cyclization of short cationic anticancer peptides containing a lipophilic β2,2‐amino acid

We have recently reported a series of synthetic anticancer heptapeptides (H‐KKWβ^2,2WKK‐NH₂) containing a central achiral and lipophilic β^2,2‐amino acid that display low toxicity against non‐malignant cells and high proteolytic stability. In the present study, we have further investigated the effects of increasing the rigidity and amphipathicity of two of our lead heptapeptides by preparing a series of seven to five residue cyclic peptides containing the two most promising β^2,2‐amino acid derivatives as part of the central lipophilic core. The peptides were tested for anticancer activity against human Burkitt's lymphoma (Ramos cells), haemolytic activity against human red blood cells (RBC) and cytotoxicity against healthy human lung fibroblast cells (MRC‐5). The results demonstrated a considerable increase in anticancer potency following head‐to‐tail peptide cyclization, especially for the shortest derivatives lacking a tryptophan residue. High‐resolution NMR studies and molecular dynamics simulations together with an annexin‐V‐FITC and propidium iodide fluorescent assay showed that the peptides had a membrane disruptive mode of action and that the more potent peptides penetrated deeper into the lipid bilayer. The need for new anticancer drugs with novel modes of action is demanding, and development of short cyclic anticancer peptides with an overall rigidified and amphipathic structure is a promising approach to new anticancer agents. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Wine phenolic compounds influence the production of volatile phenols by wine-related lactic acid bacteria

Aims: To evaluate the effect of wine phenolic compounds on the production of volatile phenols (4‐vinylphenol [4VP] and 4‐ethylphenol [4EP]) from the metabolism of p‐coumaric acid by lactic acid bacteria (LAB). Methods and Results: Lactobacillus plantarum, Lactobacillus collinoides and Pediococcus pentosaceus were grown in MRS medium supplemented with p‐coumaric acid, in the presence of different phenolic compounds: nonflavonoids (hydroxycinnamic and benzoic acids) and flavonoids (flavonols and flavanols). The inducibility of the enzymes involved in the p‐coumaric acid metabolism was studied in resting cells. The hydroxycinnamic acids tested stimulated the capacity of LAB to synthesize volatile phenols. Growth in the presence of hydroxycinnamic acids, especially caffeic acid, induced the production of 4VP by resting cells. The hydroxybenzoic acids did not significantly affect the behaviour of the studied strains. Some of the flavonoids showed an effect on the production of volatile phenols, although strongly dependent on the bacterial species. Relatively high concentrations (1 g l^?1) of tannins inhibited the synthesis of 4VP by Lact. plantarum. Conclusions: Hydroxycinnamic acids were the main compounds stimulating the production of volatile phenols by LAB. The results suggest that caffeic and ferulic acids induce the synthesis of the cinnamate decarboxylase involved in the metabolism of p‐coumaric acid. On the other hand, tannins exert an inhibitory effect. Significance and Impact of the Study: This study highlights the capacity of LAB to produce volatile phenols and that this activity is markedly influenced by the phenolic composition of the medium.     

Isolation,identification and characterization of soil microbes which degrade phenolic allelochemicals

Aims: To isolate and characterize microbes in the soils containing high contents of phenolics and to dissolve the allelopathic inhibition of plants through microbial degradation. Methods and Results: Four microbes were isolated from plant soils using a screening medium containing p‐coumaric acid as sole carbon source. The isolates were identified by biochemical analysis and sequences of their 16S or 18S rDNA, and designated as Pseudomonas putida 4CD1 from rice (Oryza sativa) soil, Ps. putida 4CD3 from pine (Pinus massoniana) soil, Pseudomonas nitroreducens 4CD2 and Rhodotorula glutinis 4CD4 from bamboo (Bambusa chungii) soil. All isolates degraded 1 g l^?1 of p‐coumaric acid by 70–93% in inorganic and by 99% in Luria‐Bertani solutions within 48 h. They also effectively degraded ferulic acid, p‐hydroxybenzoic acid and p‐hydroxybenzaldehyde. The microbes can degrade p‐coumaric acid and reverse its inhibition on seed germination and seedling growth in culture solutions and soils. Low pHs inhibited the growth and phenolic degradation of the three bacteria. High temperature inhibited the R. glutinis. Co²⁺ completely inhibited the three bacteria, but not the R. glutinis. Cu²⁺, Al³⁺, Zn²⁺, Fe³⁺, Mn²⁺, Mg²⁺ and Ca²⁺ had varying degrees of inhibition for each of the bacteria. Conclusions: Phenolics in plant culture solutions and soils can be decomposed through application of soil microbes in laboratory or controlled conditions. However, modification of growth conditions is more important for acidic and ions‐contaminated media. Significance and Impact of the Study: The four microbes were first isolated and characterized from the soils of bamboo, rice or pine. This study provides some evidence and methods for microbial control of phenolic allelochemicals.     

Oxalyltransferase,a plant cell‐wall acyltransferase activity,transfers oxalate groups from ascorbate metabolites to carbohydrates

In the plant apoplast, ascorbate is oxidised, via dehydroascorbic acid, to O‐oxalyl esters [oxalyl‐l ‐threonate (OxT) and cyclic oxalyl‐l ‐threonate (cOxT)]. We tested whether OxT and cOxT can donate the oxalyl group in transacylation reactions to form oxalyl‐polysaccharides, potentially modifying the cell wall. [oxalyl‐¹⁴C]OxT was incubated with living spinach (Spinacia oleracea) and Arabidopsis cell‐suspension cultures in the presence or absence of proposed acceptor substrates (carbohydrates). In addition, [¹⁴C]OxT and [¹⁴C]cOxT were incubated in vitro with cell‐wall enzyme preparations plus proposed acceptor substrates. Radioactive products were monitored electrophoretically. Oxalyltransferase activity was detected. Living cells incorporated oxalate groups from OxT into cell‐wall polymers via ester bonds. When sugars were added, [¹⁴C]oxalyl‐sugars were formed, in competition with OxT hydrolysis. Preferred acceptor substrates were carbohydrates possessing primary alcohols e.g. glucose. A model transacylation product, [¹⁴C]oxalyl‐glucose, was relatively stable in vivo (half‐life >24 h), whereas [¹⁴C]OxT underwent rapid turnover (half‐life ~6 h). Ionically wall‐bound enzymes catalysed similar transacylation reactions in vitro with OxT or cOxT as oxalyl donor substrates and any of a range of sugars or hemicelluloses as acceptor substrates. Glucosamine was O‐oxalylated, not N‐oxalylated. We conclude that plants possess apoplastic acyltransferase (oxalyltransferase) activity that transfers oxalyl groups from ascorbate catabolites to carbohydrates, forming relatively long‐lived O‐oxalyl‐carbohydrates. The findings increase the range of known metabolites whose accumulation in vivo indicates vitamin C catabolism. Possible signalling roles of the resulting oxalyl‐sugars can now be investigated, as can the potential ability of polysaccharide oxalylation to modify the wall's physical properties.