Dataset Information

Ribose-5-phosphate biosynthesis in Methanocaldococcus jannaschii occurs in the absence of a pentose-phosphate pathway.

ABSTRACT: Recent work has raised a question as to the involvement of erythrose-4-phosphate, a product of the pentose phosphate pathway, in the metabolism of the methanogenic archaea (R. H. White, Biochemistry 43:7618-7627, 2004). To address the possible absence of erythrose-4-phosphate in Methanocaldococcus jannaschii, we have assayed cell extracts of this methanogen for the presence of this and other intermediates in the pentose phosphate pathway and have determined and compared the labeling patterns of sugar phosphates derived metabolically from [6,6-2H2]- and [U-13C]-labeled glucose-6-phosphate incubated with cell extracts. The results of this work have established the absence of pentose phosphate pathway intermediates erythrose-4-phosphate, xylose-5-phosphate, and sedoheptulose-7-phosphate in these cells and the presence of D-arabino-3-hexulose-6-phosphate, an intermediate in the ribulose monophosphate pathway. The labeling of the D-ara-bino-3-hexulose-6-phosphate, as well as the other sugar-Ps, indicates that this hexose-6-phosphate was the precursor to ribulose-5-phosphate that in turn was converted into ribose-5-phosphate by ribose-5-phosphate isomerase. Additional work has demonstrated that ribulose-5-phosphate is derived by the loss of formaldehyde from D-arabino-3-hexulose-6-phosphate, catalyzed by the protein product of the MJ1447 gene.

SUBMITTER: Grochowski LL

PROVIDER: S-EPMC1273003 | biostudies-literature | 2005 Nov

REPOSITORIES: biostudies-literature

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Ribose-5-phosphate biosynthesis in Methanocaldococcus jannaschii occurs in the absence of a pentose-phosphate pathway.

Grochowski Laura L LL Xu Huimin H White Robert H RH

Journal of bacteriology 20051101 21

Recent work has raised a question as to the involvement of erythrose-4-phosphate, a product of the pentose phosphate pathway, in the metabolism of the methanogenic archaea (R. H. White, Biochemistry 43:7618-7627, 2004). To address the possible absence of erythrose-4-phosphate in Methanocaldococcus jannaschii, we have assayed cell extracts of this methanogen for the presence of this and other intermediates in the pentose phosphate pathway and have determined and compared the labeling patterns of ...[more]

PMID: 16237021

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Project description:UnlabelledAll methanofuran structural variants contain a basic core structure of 4-[N-(γ-l-glutamyl)-p-(β-aminoethyl)phenoxymethyl]-(aminomethyl)furan (APMF-Glu) but have different side chains depending on the source organism. Recently, we identified four genes (MfnA, MfnB, MfnC, and MfnD) that are responsible for the biosynthesis of the methanofuran precursor γ-glutamyltyramine and 5-(aminomethyl)-3-furanmethanol-phosphate (F1-P) from tyrosine, glutamate, glyceraldehyde-3-P, and alanine in Methanocaldococcus jannaschii. How γ-glutamyltyramine and F1-P couple together to form the core structure of methanofuran was previously unknown. Here, we report the identification of two enzymes encoded by the genes mj0458 and mj0840 that catalyze the formation of F1-PP from ATP and F1-P and the condensation of F1-PP with γ-glutamyltyramine, respectively, to form APMF-Glu. We have annotated these enzymes as MfnE and MfnF, respectively, representing the fifth and sixth enzymes in the methanofuran biosynthetic pathway to be identified. Although MfnE was previously reported as an archaeal adenylate kinase, our present results show that MfnE is a promiscuous enzyme and that its possible physiological role is to produce F1-PP. Unlike other enzymes catalyzing coupling reactions involving pyrophosphate as the leaving group, MfnF exhibits a distinctive α/β two-layer sandwich structure. By comparing MfnF with thiamine synthase and dihydropteroate synthase, a substitution nucleophilic unimolecular (SN-1) reaction mechanism is proposed for MfnF. With the identification of MfnE and MfnF, the biosynthetic pathway for the methanofuran core structure APMF-Glu is complete.ImportanceThis work describes the identification of the final two enzymes responsible for catalyzing the biosynthesis of the core structure of methanofuran. The gene products of mj0458 and mj0840 catalyze the formation of F1-PP and the coupling of F1-PP with γ-glutamyltyramine, respectively, to form APMF-Glu. Although the chemistry of such a coupling reaction is widespread in biochemistry, we provide here the first evidence that such a mechanism is used in methanofuran biosynthesis. MfnF belongs to the hydantoinase A family (PF01968) and exhibits a unique α/β two-layer sandwich structure that is different from the enzymes catalyzing similar reactions. Our results show that MfnF catalyzes the formation of an ether bond during methanofuran biosynthesis. Therefore, this work further expands the functionality of this enzyme family.

Dataset Information

Ribose-5-phosphate biosynthesis in Methanocaldococcus jannaschii occurs in the absence of a pentose-phosphate pathway.

Publications

Ribose-5-phosphate biosynthesis in Methanocaldococcus jannaschii occurs in the absence of a pentose-phosphate pathway.

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