Abstract
Glycoconjugates are the most diverse biomolecules of life. Mostly located at the cell surface, they translate into cell-specific “barcodes” and offer a vast repertoire of functions, including support of cellular physiology, lifestyle, and pathogenicity. Functions can be fine-tuned by non-carbohydrate modifications on the constituting monosaccharides. Among these modifications is pyruvylation, which is present either in enol or ketal form. The most commonly best-understood example of pyruvylation is enol-pyruvylation of N-acetylglucosamine, which occurs at an early stage in the biosynthesis of the bacterial cell wall component peptidoglycan. Ketal-pyruvylation, in contrast, is present in diverse classes of glycoconjugates, from bacteria to algae to yeast—but not in humans. Mild purification strategies preventing the loss of the acid-labile ketal-pyruvyl group have led to a collection of elucidated pyruvylated glycan structures. However, knowledge of involved pyruvyltransferases creating a ring structure on various monosaccharides is scarce, mainly due to the lack of knowledge of fingerprint motifs of these enzymes and the unavailability of genome sequences of the organisms undergoing pyruvylation. This review compiles the current information on the widespread but under-investigated ketal-pyruvylation of monosaccharides, starting with different classes of pyruvylated glycoconjugates and associated functions, leading to pyruvyltransferases, their specificity and sequence space, and insight into pyruvate analytics.
Highlights
Pyruvylation is a widespread non-carbohydrate modification of monosaccharides found in various classes of glycoconjugates
Conceivable to assume that more pyruvyltransferase sequences and organisms harbouring a pyruvyltransferase gene exist, which are not covered in this study
Pyruvyltransferases are a widespread but little investigated class of carbohydrate-active enzymes, which transfer a pyruvate moiety from a PEP donor to various monosaccharide targets (Table 1)
Summary
Pyruvylation is a widespread non-carbohydrate modification of monosaccharides found in various classes of glycoconjugates. The modification is present as a pyruvate (Pyr) ketal (cyclic acetal/ketal) bridging two hydroxyl groups of a monosaccharide residue and forming a ring structure [1], where pyruvate is most frequently placed across the 2,3-, 4,6-, or 3,4-positions (Figure 1I–III). The best-known example of pyruvylation, occurs as enol pyruvate (Figure 1IV), which is elaborated during the biosynthesis of the bacterial cell wall component peptidoglycan [2]. In both modes of pyruvylation, a dedicated pyruvyltransferase catalyses the transfer of the pyruvate moiety to the monosaccharide target.
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