Guanosine diphosphate mannose or GDP-mannose is a nucleotide sugar that is a substrate for glycosyltransferase reactions in metabolism.

This compound is a substrate for enzymes called mannosyltransferases.

Known as donor of activated mannose in all glycolytic reactions, GDP-mannose is essential in eukaryotes.

[1] GDP-mannose is produced from GTP and mannose-6-phosphate by the enzyme mannose-1-phosphate guanylyltransferase (GDP-mannose pyrophosphorylase, GDP-MP).

[2] This enzyme belongs to a family of nucleotidyl-transferases and is a pervasive enzyme found in bacteria, fungi, plants, and animals.