Enzymatic Synthesis of Sialic Acid 9-Phosphates

Roseman, Saul; Jourdian, George W.; Watson, Donald R.; Rood, Richard B.

doi:10.1073/pnas.47.7.958

Cited by 81 publications

(26 citation statements)

References 8 publications

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“…Synthesis of N-acylneuraminic acids in eukaryotes has been studied extensively for the last 40 years (35,(47)(48)(49)(50)(51)(52)(53)(54), and reviewed in Refs. 55 and 56).…”

Section: Discussionmentioning

confidence: 99%

Biosynthesis of KDN (2-Keto-3-deoxy-d-glycero -d-galacto -nononic acid)

Angata¹,

Nakata²,

Matsuda³

et al. 1999

Journal of Biological Chemistry

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Although the deaminoneuraminic acid or KDN glycotope (2-keto-3-deoxy-D-glycero-D-galacto-nononic acid)is expressed in glycoconjugates that range in evolutionary diversity from bacteria to man, there is little information as to how this novel sugar is synthesized. Accordingly, biosynthetic studies were initiated in trout testis, an organ rich in KDN, to determine how this sialic acid is formed. These studies have shown that the pathway consists of the following three sequential reactions: 1) Man ؉ ATP 3 Man-6-P ؉ ADP; 2) Man-6-P ؉ PEP 3 KDN-9-P ؉ Pi; 3) KDN-9-P 3 KDN ؉ Pi. Reaction 1, catalyzed by a hexokinase, is the 6-O-phosphorylation of mannose to form D-mannose 6-phosphate (Man-6-P). Reaction 2, catalyzed by KDN-9-phosphate (KDN-9-P) synthetase, condenses Man-6-P and phosphoenolpyruvate (PEP) to form KDN-9-P. Reaction 3, catalyzed by a phosphatase, is the dephosphorylation of KDN-9-P to yield free KDN. It is not known if a kinase specific for Man (Reaction 1) and a phosphatase specific for KDN-9-P (Reaction 3) may exist in tissues actively synthesizing KDN. In this study, the KDN-9-P synthetase, an enzyme that has not been previously described, was identified as at least one key enzyme that is specific for the KDN biosynthetic pathway. This enzyme was purified 50-fold from rainbow trout testis and characterized. The molecular weight of the enzyme was estimated to be about 80,000, and activity was maximum at neutral pH in the presence of Mn 2؉ . N-Acetylneuraminic acid 9-phosphate (Neu5Ac-9-P) synthetase, which catalyzes the condensation of N-acetyl-D-mannosamine 6-phosphate and phosphoenol-pyruvate to produce Neu5Ac-9-P, was co-purified with the KDN-9-P synthetase. Substrate competition experiments revealed, however, that syntheses of KDN-9-P and Neu5Ac-9-P were catalyzed by two separate synthetase activities. The significance of these studies takes on added importance with the recent discovery that the level of free KDN is elevated in human fetal cord but not matched adult red blood cells and (25), , and KDN residue-cleaving sialidases (29 -31), have been identified and partially characterized, and their similarity and dissimilarity to the metabolism of Neu5Acyl residues have been described. In marked contrast, nothing is known concerning how the KDN monosaccharide is synthesized. Two pathways are possible for synthesis of the KDN monomer. First, it could be formed directly from Neu5Ac by deacylation and deamination. Alternatively, it could arise by de novo synthesis via enzymes different from those required for synthesis of Neu5Ac. However, no evidence for the direct conversion of Neu5Ac to KDN has been obtained in any tissue homogenates examined to date. Thus, de novo synthesis by a separate pathway appears to be plausible by analogy with synthesis of other ulosonic acids. For example, 3-deoxy-D-arabino-heptulosonic acid 7-phosphate, a biosynthetic precursor of aromatic amino acids (32), 3-deoxy-D-manno-octulosonic acid, a constituent of bacterial lipopolysaccharides (33, 34) and Neu5Ac (35) are synthesi...

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“…Synthesis of N-acylneuraminic acids in eukaryotes has been studied extensively for the last 40 years (35,(47)(48)(49)(50)(51)(52)(53)(54), and reviewed in Refs. 55 and 56).…”

Section: Discussionmentioning

confidence: 99%

Biosynthesis of KDN (2-Keto-3-deoxy-d-glycero -d-galacto -nononic acid)

Angata¹,

Nakata²,

Matsuda³

et al. 1999

Journal of Biological Chemistry

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“…While the N-terminal catalytic domain of this enzyme is homologous with its E. coli NeuA counterpart, the mammalian enzyme's C-terminal domain is suggested to be a phosphatase (mentioned above in "De novo synthesis") that regulates synthetase activity through potential dephosphorylation of the N-terminal catalytic domain. However, Krapp et al (2003) did not detect phosphate residues in the N-terminal domain and it seems equally valid to speculate that the putative phosphatase domain converts the Neu5Ac-9-P precursor to the obligate-free Neu5Ac substrate prior to the activation reaction (111). Because the pathway of sialic acid synthesis in E. coli does not include the phosphorylated Neu5Ac intermediate (Fig.…”

Section: Addendum In Proofmentioning

confidence: 99%

“…In mammals, the UDP-GlcNAc epimerase is homologous with NeuC (103), and the mammalian orthologue of NeuB uses ManNAc-6-P instead of free ManNAc for condensation with phosphoenolpyruvate. The sialic acid-9-P produced by mammalian NeuB must be dephosphorylated prior to activation by NeuA (111). Although the identity of this phosphatase is unknown, the C-terminal domain of mammalian NeuA is homologous with a phosphatase (YrbI) that has been shown to dephosphorylate KDO-8-P as a necessary prior step to CMP-KDO synthesis (164).…”

Section: De Novo Synthesismentioning

confidence: 99%

Diversity of Microbial Sialic Acid Metabolism

Vimr

Kalivoda

Deszo

et al. 2004

Microbiol Mol Biol Rev

507

663

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Sialic acids are structurally unique nine-carbon keto sugars occupying the interface between the host and commensal or pathogenic microorganisms. An important function of host sialic acid is to regulate innate immunity, and microbes have evolved various strategies for subverting this process by decorating their surfaces with sialylated oligosaccharides that mimic those of the host. These subversive strategies include a de novo synthetic pathway and at least two truncated pathways that depend on scavenging host-derived intermediates. A fourth strategy involves modification of sialidases so that instead of transferring sialic acid to water (hydrolysis), a second active site is created for binding alternative acceptors. Sialic acids also are excellent sources of carbon, nitrogen, energy, and precursors of cell wall biosynthesis. The catabolic strategies for exploiting host sialic acids as nutritional sources are as diverse as the biosynthetic mechanisms, including examples of horizontal gene transfer and multiple transport systems. Finally, as compounds coating the surfaces of virtually every vertebrate cell, sialic acids provide information about the host environment that, at least in Escherichia coli, is interpreted by the global regulator encoded by nanR. In addition to regulating the catabolism of sialic acids through the nan operon, NanR controls at least two other operons of unknown function and appears to participate in the regulation of type 1 fimbrial phase variation. Sialic acid is, therefore, a host molecule to be copied (molecular mimicry), eaten (nutrition), and interpreted (cell signaling) by diverse metabolic machinery in all major groups of mammalian pathogens and commensals

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“…The activated form of pyruvate, phospho enol pyruvate (PEP), is derived from glycolysis. The Neu5Ac-9-phosphate synthase uses ManNAc-6-phosphate instead of ManNAc, and catalyzes an aldol addition with PEP for the formation of Neu5Ac-9-phosphate [5]. The reaction is thereby driven by the release of the phosphate group from PEP.…”

Section: Sialic Acid Biosynthesis Pathwaymentioning

confidence: 99%