galactose metabolic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways involving galactose, the aldohexose galacto-hexose. D-galactose is widely distributed in combined form in plants, animals and microorganisms as a constituent of oligo- and polysaccharides; it also occurs in galactolipids and as its glucoside in lactose and melibiose. [ISBN:0198506732]

Galactose metabolism is a fundamental biological process that converts galactose, a simple sugar found in milk and other dairy products, into glucose, the primary energy source for cells. The process involves a series of enzymatic reactions, primarily within the liver, and is crucial for maintaining energy homeostasis and preventing galactose accumulation.

The initial step involves the phosphorylation of galactose by galactokinase, converting it to galactose-1-phosphate. This is followed by the transfer of a UDP moiety from UDP-glucose to galactose-1-phosphate by galactose-1-phosphate uridyltransferase (GALT), producing UDP-galactose and glucose-1-phosphate. UDP-galactose then undergoes an epimerization reaction catalyzed by UDP-galactose 4-epimerase, yielding UDP-glucose. This step is essential as it ensures the recycling of UDP-glucose for subsequent rounds of galactose metabolism. Finally, the glucose-1-phosphate generated is converted to glucose-6-phosphate, entering the glycolytic pathway for energy production.

Defects in the galactose metabolic pathway can lead to various diseases, most notably galactosemia. This genetic disorder arises from mutations in genes encoding enzymes involved in galactose metabolism, particularly GALT. Without proper GALT function, galactose-1-phosphate accumulates, leading to liver damage, mental retardation, and other complications.

In summary, galactose metabolism is a tightly regulated and vital process responsible for the conversion of galactose into glucose. This pathway is crucial for energy production and maintaining cellular homeostasis. Disruptions in this process can lead to serious health consequences, emphasizing the importance of understanding and addressing galactose metabolic disorders.'
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