Effects of tetrahydrofolate polyglutamates on the kinetic parameters of serine hydroxymethyltransferase and glycine decarboxylase from pea leaf mitochondria

Besson, Véronique; Rébeillé, Fabrice; Neuburger, Michel; Douce, Roland; Cossins, Edwin A.

doi:10.1042/bj2920425

Cited by 63 publications

(54 citation statements)

References 22 publications

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“…Tliis fraction, as judged by the presence of marker enzymes (Table 3), had only minor mitochondrial or chloroplastic contamination. The cytosolic folate pool, like that of rat liver (24) rhe purified mitochondrial fraction contained a smaller proportion of the celiular folate pooI and, in agreement with an eariier study (39), these were highiy variable between individual cxtracts. IIPLC analyses showed that mitochondrial folates were mainly 5-HCO-H4PteGlu and H4PteGlu derivatives, a fmding similar to that of rat pancreas mitochondria (40).…”

Section: Intracellular Folatesupporting

confidence: 54%

The Intracellular Distribution of Folate Derivatives in Pea Leaves

2003

Pteridines

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After hydrolysis of polyglutamate derivatives, leaf extracts of pea (Pisum sativum L.) seedlings were examined for individual folates using high Performance liquid chromatography and microbiological assays employing Lactobacillus rhamnosus and Pediococcus acidilactici. 14-day seedlings contained 0.17±0.01 nmol folate mg' protem that was predominantly methylated and associated with the cytosolic fraction. Percoll gradient-purified mitochondria and chloroplasts contained 11.0±2.3% and 8.4±0.6% of cellular folate, respectively. Mitochondrial folates {0.47±0.11 nmol folate mg' protein) were predominately (90%) formylated and unsubstituted. In contrast, chloroplasts contained a less concentrated (0.02±0.001 nmol folate mg ' protein) folate pool consisting of approximately 30% methylated folate. The total folate content of pea leaves increased by 40% when dark-grown (etiolated) 9-day seedlings were exposed to light for 48 hours. Duriiig this light treatment, the mitochondrial folate pool, on a per mg protein basis, increased 10-fold. This light treatment also changed the composition of the mitochondrial folate pool with a shift occurring from methylated to formylated and unsubstituted derivatives. These changes in the folates of greening tissues are discussed in relation to the metabolism of glycine and serine that accompanies photorespiration in leaf tissues.

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Section: Intracellular Folatesupporting

confidence: 54%

The Intracellular Distribution of Folate Derivatives in Pea Leaves

2003

Pteridines

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“…3 and 4 that the mitochondria contain ϳ50% of the total 5-CHO-THF in wild type leaves and Ն80% in mutant leaves. The basis for intramitochondrial retention of 5-CHO-THF may be that it is polyglutamylated, as are the bulk of mitochondrial folates (40), and that mitochondrial folate transporters prefer monoglutamates, as do most other folate carriers (41). Keeping much of the 5-CHO-THF inside mitochondria clearly reduces its potential to interfere with cytosolic or plastidial isoforms of folate enzymes.…”

Section: -Formyltetrahydrofolate In Arabidopsismentioning

confidence: 99%

5-Formyltetrahydrofolate Is an Inhibitory but Well Tolerated Metabolite in Arabidopsis Leaves

Goyer

Collakova

Garza

et al. 2005

Journal of Biological Chemistry

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5-Formyltetrahydrofolate (5-CHO-THF) is formed viaa second catalytic activity of serine hydroxymethyltransferase (SHMT) and strongly inhibits SHMT and other folate-dependent enzymes in vitro. The only enzyme known to metabolize 5-CHO-THF is 5-CHO-THF cycloligase (5-FCL), which catalyzes its conversion to 5,10-methenyltetrahydrofolate. Because 5-FCL is mitochondrial in plants and mitochondrial SHMT is central to photorespiration, we examined the impact of an insertional mutation in the Arabidopsis 5-FCL gene (At5g13050) under photorespiratory (30 and 370 mol of CO 2 mol ؊1 ) and non-photorespiratory (3200 mol of CO 2 mol ؊1 ) conditions. The mutation had only mild visible effects at 370 mol of CO 2 mol ؊1 , reducing growth rate by ϳ20% and delaying flowering by 1 week. However, the mutation doubled leaf 5-CHO-THF level under all conditions and, under photorespiratory conditions, quadrupled the pool of 10-formyl-/5,10-methenyltetrahydrofolates (which could not be distinguished analytically). At 370 mol of CO 2 mol ؊1 , the mitochondrial 5-CHO-THF pool was 8-fold larger in the mutant and contained most of the 5-CHO-THF in the leaf. In contrast, the buildup of 10-formyl-/5,10-methenyltetrahydrofolates was extramitochondrial. In photorespiratory conditions, leaf glycine levels were up to 46-fold higher in the mutant than in the wild type. Furthermore, when leaves were supplied with 5-CHO-THF, glycine accumulated in both wild type and mutant. These data establish that 5-CHO-THF can inhibit SHMT in vivo and thereby influence glycine pool size. However, the near-normal growth of the mutant shows that even exceptionally high 5-CHO-THF levels do not much affect fluxes through SHMT or any other folate-dependent reaction, i.e. that 5-CHO-THF is well tolerated in plants. 5-Formyltetrahydrofolate (5-CHO-THF)1 is formed from 5,10-methenyltetrahydrofolate (5,10-CHϭTHF) by a hydrolytic reaction catalyzed by serine hydroxymethyltransferase (SHMT) in the presence of glycine (1, 2). Spontaneous chemical hydrolysis of 5,10-CHϭTHF may be a minor additional source (3). 5-CHO-THF is the most stable natural folate and the most enigmatic, for it is the only one that does not serve as a cofactor in one-carbon metabolism. Instead, 5-CHO-THF is a potent inhibitor of SHMT and most other folate-dependent enzymes in vitro (4, 5). 5-CHO-THF probably acts as a stable storage form of folate in seeds and fungal spores (5-7), but it is not clear what role, if any, it plays in metabolically active tissues (8). This question is particularly pertinent for leaves. Leaf mitochondria have very high levels of SHMT and, during photorespiration, receive a massive influx of glycine (which leads to a matching SHMT-mediated glycine 3 serine flux) (9). Conditions in leaf mitochondria therefore favor 5-CHO-THF formation (Fig. 1). Indeed, 5-CHO-THF can comprise 50% of the folate pool in leaf mitochondria (10, 11), which is far more than in mammalian mitochondria (12)(13)(14). Furthermore, 5-CHO-THF is reported to make up 14 -40% of the folate pool in leaves and o...

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“…The cytosol contains the largest pool of folates, predominantly in the form of polyglutamylated methyl derivatives. In pea leaves, mitochondria and chloroplasts also contain principally (Ͼ90%) polyglutamylated forms (5,6). The distribution of folates among the organelles is unequal because the estimated concentration of folates in mitochondria is 100-150-fold higher than in chloroplasts (7,8).…”

mentioning

confidence: 99%

“…5). Serine hydroxymethyltransferase, the enzyme catalyzing the conversion of serine to glycine with the concomitant formation of 5,10-CH 2 -H 4 F from unsubstituted H 4 F, is found in these three compartments (33) and exhibits a marked preference for polyglutamate coenzymes (6). Also, the mitochondria, the cytosol, and the chloroplast each contain a parallel set of enzymes catalyzing the interconversion of 5,10-CH 2 -, 5,10-CH ϩ -, and 10-CHO-substituted folate coenzymes (7,34).…”

mentioning

confidence: 99%

“…It is an absolute requirement for the synthesis of purine, thymidylate, formylmethionyltRNA, pantothenate, and methionine, and for the interconversion of glycine and serine. The tetrahydrofolate molecule [5,6,7,8-tetrahydropteroylpoly-␥-glutamate (H 4 F-Glu n )] capable of carrying and donating C1 units consists chemically of a pteridine ring attached to a para aminobenzoic acid (p-ABA) moiety, which in turn is attached to glutamate residues. Because the affinity of folate-dependent enzymes increases markedly with the number of glutamate residues, the folylpolyglutamates are the preferred coenzymes of C1 metabolism (reviewed in refs.…”

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confidence: 99%

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Tetrahydrofolate biosynthesis in plants: Molecular and functional characterization of dihydrofolate synthetase and three isoforms of folylpolyglutamate synthetase in Arabidopsis thaliana

Ravanel

Cherest

Jabrin

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

130

155

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Tetrahydrofolate coenzymes involved in one-carbon (C1) metabolism are polyglutamylated. In organisms that synthesize tetrahydrofolate de novo, dihydrofolate synthetase (DHFS) and folylpolyglutamate synthetase (FPGS) catalyze the attachment of glutamate residues to the folate molecule. In this study we isolated cDNAs coding a DHFS and three isoforms of FPGS from Arabidopsis thaliana. The function of each enzyme was demonstrated by complementation of yeast mutants deficient in DHFS or FPGS activity, and by measuring in vitro glutamate incorporation into dihydrofolate or tetrahydrofolate. DHFS is present exclusively in the mitochondria, making this compartment the sole site of synthesis of dihydrofolate in the plant cell. In contrast, FPGS is present as distinct isoforms in the mitochondria, the cytosol, and the chloroplast. Each isoform is encoded by a separate gene, a situation that is unique among eukaryotes. The compartmentation of FPGS isoforms is in agreement with the predominance of ␥-glutamylconjugated tetrahydrofolate derivatives and the presence of serine hydroxymethyltransferase and C1-tetrahydrofolate interconverting enzymes in the cytosol, the mitochondria, and the plastids. Thus, the combination of FPGS with these folate-mediated reactions can supply each compartment with the polyglutamylated folate coenzymes required for the reactions of C1 metabolism. Also, the multicompartmentation of FPGS in the plant cell suggests that the transported forms of folate are unconjugated.

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Effects of tetrahydrofolate polyglutamates on the kinetic parameters of serine hydroxymethyltransferase and glycine decarboxylase from pea leaf mitochondria

Cited by 63 publications

References 22 publications

The Intracellular Distribution of Folate Derivatives in Pea Leaves

The Intracellular Distribution of Folate Derivatives in Pea Leaves

5-Formyltetrahydrofolate Is an Inhibitory but Well Tolerated Metabolite in Arabidopsis Leaves

Tetrahydrofolate biosynthesis in plants: Molecular and functional characterization of dihydrofolate synthetase and three isoforms of folylpolyglutamate synthetase in Arabidopsis thaliana

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