The Leloir pathway is a

metabolic pathway In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reac ...

for the catabolism of D-galactose. It is named after

Luis Federico Leloir Luis Federico Leloir (September 6, 1906 – December 2, 1987) was an Argentine physician and biochemist who received the 1970 Nobel Prize in Chemistry for his discovery of the metabolic pathways in lactose. Although born in France, Leloir r ...

, who first described it. Leloir pathway

In the first step, galactose mutarotase facilitates the conversion of β-D-galactose to α-D-galactose since this is the active form in the pathway. Next, α-D-galactose is

phosphorylated In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, whi ...

galactokinase Galactokinase is an enzyme (phosphotransferase) that facilitates the phosphorylation of α-D-galactose to galactose 1-phosphate at the expense of one molecule of ATP. Galactokinase catalyzes the second step of the Leloir pathway, a metabolic p ...

galactose 1-phosphate D-Galactose-1-phosphate is an intermediate in the intraconversion of glucose and uridine diphosphate galactose. It is formed from galactose by galactokinase.The improper metabolism of galactose-1-phosphate is a characteristic of galactosemia. The ...

. In the third step, D-galactose-1-phosphate uridylyltransferase converts galactose 1-phosphate to

UDP-galactose Uridine diphosphate galactose ( UDP- galactose) is an intermediate in the production of polysaccharides. It is important in nucleotide sugars metabolism, and is the substrate for the transferase B4GALT5. See also * Galactose * UDP galactose e ...

using

UDP-glucose Uridine diphosphate glucose (uracil-diphosphate glucose, UDP-glucose) is a nucleotide sugar. It is involved in glycosyltransferase reactions in metabolism. Functions UDP-glucose is used in nucleotide sugar metabolism as an activated form of glu ...

as the

uridine diphosphate Uridine diphosphate, abbreviated UDP, is a nucleotide diphosphate. It is an ester of pyrophosphoric acid with the nucleoside uridine. UDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase uracil. UDP is an importa ...

source. Finally, UDP-galactose 4-epimerase recycles the UDP-galactose to UDP-glucose for the transferase reaction. Additionally,

phosphoglucomutase Phosphoglucomutase () is an enzyme that transfers a phosphate group on an α-D-glucose monomer from the 1 to the 6 position in the forward direction or the 6 to the 1 position in the reverse direction. More precisely, it facilitates the interconve ...

converts the D-glucose 1-phosphate to D-glucose 6-phosphate.

References

{{Reflist, refs= * {{cite journal , vauthors=Holden HM, Rayment I, Thoden JB , title = Structure and function of enzymes of the Leloir pathway for galactose metabolism , journal = J. Biol. Chem. , volume = 278 , issue = 45 , pages = 43885–8 , date=November 2003 , pmid = 12923184 , doi = 10.1074/jbc.R300025200 , doi-access = free * {{cite journal , author=Frey PA , title=The Leloir pathway: a mechanistic imperative for three enzymes to change the stereochemical configuration of a single carbon in galactose , journal=FASEB J. , volume=10 , issue=4 , pages=461–70 , date=March 1996 , pmid=8647345 , doi= 10.1096/fasebj.10.4.8647345, s2cid=13857006 , url=http://www.fasebj.org/cgi/pmidlookup?view=long&pmid=8647345 , access-date=2011-04-01 Metabolism Inborn errors of metabolism Galactose