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.

Trypanosoma cruzi contains two galactokinases; molecular and biochemical characterization

“…In L. major both pathways are active and contribute to the UDP-Gal synthesis [14,15]. In contrast, the T. brucei genome lacks a homologue of the USP gene and it has a pseudogene of GALK [12].…”

Structural Basis for the Broad Substrate Range of the UDP-Sugar Pyrophosphorylase from Leishmania major

“…Galactose is likely to be converted into Gal-1-P by the putative galactokinase present in the genome of Leishmania major (LmjF35.2740) and subsequently activated into UDP-Gal by an unusual UDP-sugar pyrophosphorylase (USP; EC 2.7.7.64) recently identified in L. major as well as in T. cruzi. [17][18][19] Like plant USPs, the leishmanial enzyme exhibits broad in vitro specificity but preferentially activates Gal-1-P and Glc-1-P. 17,[20][21][22] In L. major, deletion of UGP leads to a mild phenotype associated with residual UGP activity likely due to USP. 19 Similarly, USP seems to partially compensate for deficiency of UGPs in plants.…”

“…[17][18][19] Like plant USPs, the leishmanial enzyme exhibits broad in vitro specificity but preferentially activates Gal-1-P and Glc-1-P. 17,[20][21][22] In L. major, deletion of UGP leads to a mild phenotype associated with residual UGP activity likely due to USP. 19 Similarly, USP seems to partially compensate for deficiency of UGPs in plants. 23,24 In vivo, it likely plays a role in the salvage of several monosaccharides and is essential for pollen development.…”

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2009–2010

“…(Paściak et al, 2010b) Aspergillus fumigatus Glycoinositolphospho-ceramides TOF The mitA gene shown to be required for mannosylation (Kotz et al, 2010) Hymenobacter sp. Carotenoids MALDI Identification of 2'-methyl and 1'-xylosyl derivatives of 2'hydroxyflexixanthin (Klassen et al, 2009) Leishmania major Glycoinositolphospholipids TOF (CHCA), ESI-MS n Demonstration of a UDPglucose independent UDPgalactose salvage pathway (Lamerz et al, 2010)…”