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Intermediates and enzymes in the Leloir pathway of galactose metabolism [5] 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 by galactokinase to galactose 1-phosphate.
The main pathway of galactose metabolism is the Leloir pathway; humans and other species, however, have been noted to contain several alternate pathways, such as the De Ley Doudoroff Pathway. The Leloir pathway consists of the latter stage of a two-part process that converts β-D-galactose to UDP-glucose. The initial stage is the conversion of ...
After separation from glucose, galactose travels to the liver for conversion to glucose. [12] Galactokinase uses one molecule of ATP to phosphorylate galactose. [2] The phosphorylated galactose is then converted to glucose-1-phosphate, and then eventually glucose-6-phosphate, which can be broken down in glycolysis. [2]
Additionally, since the metabolism of galactose in the cell is involved in both anabolic and catabolic pathways, a novel regulatory system using two promoters for differential repression has been identified and characterized within the context of the gal operon.
Galactose addition occurs primarily through the β-1,4-galactosyltransferase enzyme (β4Gal-T1) while the enzymes responsible for β-3-Nacetylglucosamine have not been clearly identified. Finally, sulfation of the polymer occurs at the 6-position of both sugar residues.
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. [1] Galactokinase catalyzes the second step of the Leloir pathway, a metabolic pathway found in most organisms for the catabolism of α-D-galactose to glucose 1-phosphate. [2]
GALT catalyzes the second reaction of the Leloir pathway of galactose metabolism through ping pong bi-bi kinetics with a double displacement mechanism. [6] This means that the net reaction consists of two reactants and two products (see the reaction above) and it proceeds by the following mechanism: the enzyme reacts with one substrate to generate one product and a modified enzyme, which goes ...
After glycogen phosphorylase catalyzes the phosphorolytic cleavage of a glucosyl residue from the glycogen polymer, the freed glucose has a phosphate group on its 1-carbon. . This glucose 1-phosphate molecule is not itself a useful metabolic intermediate, but phosphoglucomutase catalyzes the conversion of this glucose 1-phosphate to glucose 6-phosphate (see below for the mechanism of this reactio