GNT

GnT is an abbreviation commonly used for glycosyltransferase enzymes that act on N-linked glycans in the Golgi apparatus. In many contexts, GnT refers specifically to a family of enzymes named GnT-I, GnT-II, GnT-III, GnT-IV, GnT-V, and so on, each catalyzing distinct steps in N-glycan processing. These enzymes transfer activated sugar donors, such as UDP-N-acetylglucosamine, to acceptor glycoprotein substrates, thereby shaping the branching and composition of N-glycans. The activity of GnTs influences protein folding, stability, intracellular trafficking, cell signaling, and interactions with other cells and the immune system.

In humans, several GnTs have well-characterized roles. GnT-I (encoded by MGAT1) initiates the processing of high-mannose N-glycans to complex and hybrid types, and is essential for proper maturation of many glycoproteins. GnT-II (MGAT2) further extends branching to form more elaborate structures. GnT-V (MGAT5) adds β1,6-GlcNAc branching, a modification associated with altered receptor interactions and has been linked to enhanced metastasis in cancer. GnT-III (MGAT3) introduces a bisecting GlcNAc that can interfere with subsequent processing and modify glycan function.

Regulation of GnT activity affects development, immunity, and disease. Defects in GnT activity are linked to congenital disorders of glycosylation and various pathological states, while altered GnT expression patterns have been observed in multiple cancers. GnTs remain a focus of research for understanding glycoprotein biology and for exploring therapeutic strategies aimed at modulating glycosylation. The term GnT can also be used more generally to refer to glycosyltransferases that process N-glycans, across different species.