UDPglukoosi

UDP-glukoosi (UDP-glucose) is a nucleotide sugar that serves as an activated donor of glucose in several biosynthetic pathways. It consists of glucose linked to uridine diphosphate via a pyrophosphate bridge. In cells, UDP-glukoosi is produced by UDP-glukoosi pyrophosphorylase from UTP and glucose-1-phosphate, with pyrophosphate rapidly hydrolyzed to drive the reaction forward.

Biological roles include glycogen synthesis, where glycogen synthase uses UDP-glukoosi as the glucose donor to extend the glycogen chain. It also supplies glucose for glycosylation of proteins and lipids through various glycosyltransferases in the endoplasmic reticulum and Golgi. Additionally, UDP-glukoosi is converted to UDP-glucuronic acid by UDP-glucose dehydrogenase, providing substrates for glycosaminoglycans and detoxification pathways.

Regulation and distribution: cellular levels of UDP-glukoosi reflect carbohydrate availability and energy status. The pool is maintained by synthesis via UDP-glukoosi pyrophosphorylase and consumption by glycogen synthase and glycosyltransferases, among others.

Clinical significance: proper UDP-glukoosi metabolism is essential for glycogen storage and protein and lipid glycosylation. Disruptions in the related pathways can contribute to metabolic disorders and congenital disorders of glycosylation. Diagnostic approaches may include measurement of nucleotide sugar pools and genetic testing of pathway enzymes.

See also: UDP-glucose, glycogen synthase, glycosyltransferase, UDP-glucuronic acid, congenital disorders of glycosylation.