Alpha-1,4-glucan-protein synthase (ADP-forming)

Alpha-1,4-glucan-protein synthase (ADP-forming) is an enzyme belonging to the glycosyltransferase family, specifically those that utilize a nucleotide-diphospho-sugar as the donor. It catalyzes the formation of alpha-1,4-glucan chains linked to a protein acceptor, utilizing ADP-glucose as the glucosyl donor and releasing ADP as a byproduct. This process is a form of glycosylation where a carbohydrate is attached to a protein.

The systematic name for this enzyme is ADP-glucose:protein alpha-D-glucosyltransferase.

The enzyme's primary function is to extend a pre-existing oligosaccharide chain linked to a protein, adding glucose residues in an alpha-1,4 linkage. This results in the synthesis of larger, more complex glycans attached to the protein. The specific protein to which the glycan is attached varies depending on the organism and the cellular context. The activity of this enzyme is crucial for the biosynthesis of various glycoproteins involved in diverse biological processes, including cell wall biosynthesis, protein folding, and cell signaling.

It differs from other glucan synthases in its use of ADP-glucose as the glucose donor molecule, as opposed to UDP-glucose or GDP-glucose. The specificity for ADP-glucose indicates a unique metabolic pathway and regulatory mechanism compared to other glycosyltransferases.

Further research is required to fully elucidate the enzyme's detailed mechanism, substrate specificity, and regulatory control in different organisms.