polyLacNAc

PolyLacNAc, short for poly-N-acetyllactosamine, is a polymer formed by repeating units of N-acetyllactosamine (LacNAc), a disaccharide consisting of galactose beta-1,4 linked to N-acetylglucosamine. In polyLacNAc chains the LacNAc units are extended by alternating glycosidic linkages, typically described as Galβ1-4GlcNAcβ1-3Galβ1-4GlcNAc, creating longer linear or branched chains on glycoproteins and glycolipids.

These chains are commonly found on N- and O-linked glycans in a wide range of organisms, and their length and branching can vary by tissue and developmental stage. Biosynthesis is mediated by families of glycosyltransferases, including β1-3 N-acetylglucosaminyltransferases that extend GlcNAc residues and β1-4 galactosyltransferases that add Gal residues; overall length is influenced by the expression of these enzymes, substrate availability, and capping modifications such as sialylation or fucosylation.

PolyLacNAc chains function as ligands for lectins, notably galectins, and can affect cell–cell adhesion, signaling, immune recognition, and pathogen interactions. Longer polyLacNAc chains may enhance galectin binding and receptor clustering, while variations in length or terminal modifications can alter antigenicity and microbial recognition.

Analytical approaches to polyLacNAc include lectin binding assays using LacNAc-specific lectins and mass spectrometry-based glycomic analyses. In human glycobiology, polyLacNAc serves as a versatile scaffold that can be extended or modified to generate more complex structures, including Lewis-type antigens upon further fucosylation or sialylation.

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