Transketolase

File:E4P in Transketolase Active Site.jpg

E4P in Transketolase Active Site

Enzyme involved in the pentose phosphate pathway

Transketolase

Transketolase (TKT) is an enzyme that plays a crucial role in the pentose phosphate pathway, a metabolic pathway parallel to glycolysis. It catalyzes the transfer of a two-carbon unit from a ketose donor to an aldose acceptor. This enzyme is essential for the non-oxidative phase of the pentose phosphate pathway, which is important for the production of nucleotides and nucleic acids.

Function

Transketolase catalyzes two key reactions in the pentose phosphate pathway:

1. The conversion of xylulose-5-phosphate and ribose-5-phosphate to glyceraldehyde-3-phosphate and sedoheptulose-7-phosphate.
2. The conversion of xylulose-5-phosphate and erythrose-4-phosphate to glyceraldehyde-3-phosphate and fructose-6-phosphate.

These reactions are essential for the interconversion of sugars and the generation of NADPH, which is necessary for biosynthetic reactions and antioxidant defense.

Structure

Transketolase is a homodimeric enzyme, meaning it consists of two identical subunits. Each subunit contains a binding site for the cofactor thiamine pyrophosphate (TPP), which is essential for its catalytic activity. The enzyme also requires magnesium ions for its function.

Clinical Significance

Deficiency in transketolase activity can lead to various metabolic disorders. One such condition is Wernicke-Korsakoff syndrome, a neurological disorder often associated with chronic alcoholism and characterized by a deficiency in thiamine (vitamin B1), which is a cofactor for transketolase. Symptoms include confusion, ataxia, and memory problems.

Related Enzymes

Transketolase is part of a family of enzymes that includes transaldolase, which also participates in the pentose phosphate pathway. Both enzymes work together to maintain the balance of sugar phosphates in the cell.

See Also

• Pentose phosphate pathway
• Glycolysis
• Thiamine
• NADPH
• Wernicke-Korsakoff syndrome

External Links

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