Dataset Information

Deletion of UDP-glucose pyrophosphorylase reveals a UDP-glucose independent UDP-galactose salvage pathway in Leishmania major.

ABSTRACT: The nucleotide sugar UDP-galactose (UDP-Gal) is essential for the biosynthesis of several abundant glycoconjugates forming the surface glycocalyx of the protozoan parasite Leishmania major. Current data suggest that UDP-Gal could arise de novo by epimerization of UDP-glucose (UDP-Glc) or by a salvage pathway involving phosphorylation of Gal and the action of UDP-glucose:alpha-D-galactose-1-phosphate uridylyltransferase as described by Leloir. Since both pathways require UDP-Glc, inactivation of the UDP-glucose pyrophosphorylase (UGP) catalyzing activation of glucose-1 phosphate to UDP-Glc was expected to deprive parasites of UDP-Gal required for Leishmania glycocalyx formation. Targeted deletion of the gene encoding UGP, however, only partially affected the synthesis of the Gal-rich phosphoglycans. Moreover, no alteration in the abundant Gal-containing glycoinositolphospholipids was found in the deletion mutant. Consistent with these findings, the virulence of the UGP-deficient mutant was only modestly affected. These data suggest that Leishmania elaborates a UDP-Glc independent salvage pathway for UDP-Gal biosynthesis.

SUBMITTER: Lamerz AC

PROVIDER: S-EPMC2900899 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Deletion of UDP-glucose pyrophosphorylase reveals a UDP-glucose independent UDP-galactose salvage pathway in Leishmania major.

Lamerz Anne-Christin AC Damerow Sebastian S Kleczka Barbara B Wiese Martin M van Zandbergen Ger G Lamerz Jens J Wenzel Alexander A Hsu Fong-Fu FF Turk John J Beverley Stephen M SM Routier Françoise H FH

Glycobiology 20100324 7

The nucleotide sugar UDP-galactose (UDP-Gal) is essential for the biosynthesis of several abundant glycoconjugates forming the surface glycocalyx of the protozoan parasite Leishmania major. Current data suggest that UDP-Gal could arise de novo by epimerization of UDP-glucose (UDP-Glc) or by a salvage pathway involving phosphorylation of Gal and the action of UDP-glucose:alpha-D-galactose-1-phosphate uridylyltransferase as described by Leloir. Since both pathways require UDP-Glc, inactivation of ...[more]

PMID: 20335578

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Project description:Leishmaniases are a set of tropical and sub-tropical diseases caused by protozoan parasites of the genus Leishmania whose severity ranges from self-healing cutaneous lesions to fatal visceral infections. Leishmania parasites synthesise a wide array of cell surface and secreted glycoconjugates that play important roles in infection. These glycoconjugates are particularly abundant in the promastigote form and known to be essential for establishment of infection in the insect midgut and effective transmission to the mammalian host. Since they are rich in galactose, their biosynthesis requires an ample supply of UDP-galactose. This nucleotide-sugar arises from epimerisation of UDP-glucose but also from an uncharacterised galactose salvage pathway. In this study, we evaluated the role of the newly characterised UDP-sugar pyrophosphorylase (USP) of Leishmania major in UDP-galactose biosynthesis. Upon deletion of the USP encoding gene, L. major lost the ability to synthesise UDP-galactose from galactose-1-phosphate but its ability to convert glucose-1-phosphate into UDP-glucose was fully maintained. Thus USP plays a role in UDP-galactose activation but does not significantly contribute to the de novo synthesis of UDP-glucose. Accordingly, USP was shown to be dispensable for growth and glycoconjugate biosynthesis under standard growth conditions. However, in a mutant seriously impaired in the de novo synthesis of UDP-galactose (due to deficiency of the UDP-glucose pyrophosphorylase) addition of extracellular galactose increased biosynthesis of the cell surface lipophosphoglycan. Thus under restrictive conditions, such as those encountered by Leishmania in its natural habitat, galactose salvage by USP may play a substantial role in biosynthesis of the UDP-galactose pool. We hypothesise that USP recycles galactose from the blood meal within the midgut of the insect for synthesis of the promastigote glycocalyx and thereby contributes to successful vector infection.

Project description:In animals, the main precursor for glycosaminoglycan and furthermore proteoglycan biosynthesis, like hyaluronic acid, is UDP-glucuronic acid, which is synthesized via the nucleotide sugar oxidation pathway. Mutations in this pathway cause severe developmental defects (deficiency in the initiation of heart valve formation). In plants, UDP-glucuronic acid is synthesized via two independent pathways. Beside the nucleotide sugar oxidation pathway, a second minor route to UDP-glucuronic acid exist termed the myo-inositol oxygenation pathway. Within this myo-inositol is ring cleaved into glucuronic acid, which is subsequently converted to UDP-glucuronic acid by glucuronokinase and UDP-sugar pyrophosphorylase. Here we report on a similar, but bifunctional enzyme from zebrafish (Danio rerio) which has glucuronokinase/putative pyrophosphorylase activity. The enzyme can convert glucuronic acid into UDP-glucuronic acid, required for completion of the alternative pathway to UDP-glucuronic acid via myo-inositol and thus establishes a so far unknown second route to UDP-glucuronic acid in animals. Glucuronokinase from zebrafish is a member of the GHMP-kinase superfamily having unique substrate specificity for glucuronic acid with a Km of 31 ± 8 µM and accepting ATP as the only phosphate donor (Km: 59 ± 9 µM). UDP-glucuronic acid pyrophosphorylase from zebrafish has homology to bacterial nucleotidyltransferases and requires UTP as nucleosid diphosphate donor. Genes for bifunctional glucuronokinase and putative UDP-glucuronic acid pyrophosphorylase are conserved among some groups of lower animals, including fishes, frogs, tunicates, and polychaeta, but are absent from mammals. The existence of a second pathway for UDP-glucuronic acid biosynthesis in zebrafish likely explains some previous contradictory finding in jekyll/ugdh zebrafish developmental mutants, which showed residual glycosaminoglycans and proteoglycans in knockout mutants of UDP-glucose dehydrogenase.

Dataset Information

Deletion of UDP-glucose pyrophosphorylase reveals a UDP-glucose independent UDP-galactose salvage pathway in Leishmania major.

Publications

Deletion of UDP-glucose pyrophosphorylase reveals a UDP-glucose independent UDP-galactose salvage pathway in Leishmania major.

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