Transaldolase

Transaldolase is an enzyme that plays a crucial role in the pentose phosphate pathway (PPP), a metabolic pathway involved in the production of ribose-5-phosphate and NADPH. This enzyme catalyzes the transfer of a three-carbon dihydroxyacetone unit from a ketose donor to an aldose acceptor, resulting in the formation of a four-carbon ketose and a five-carbon aldose.

Function

Transaldolase is primarily involved in the interconversion of sugars in the PPP. It transfers a dihydroxyacetone moiety from sedoheptulose-7-phosphate to glyceraldehyde-3-phosphate, resulting in the formation of erythrose-4-phosphate and fructose-6-phosphate. This reaction is reversible and is essential for the synthesis of ribose-5-phosphate, a key component in nucleotide synthesis, as well as for the generation of NADPH, an important reducing agent in various cellular processes.

Structure

Transaldolase is a homodimeric enzyme, meaning it consists of two identical subunits. Each subunit contains an active site where the catalytic reaction takes place. The active site consists of several amino acid residues that are involved in substrate binding and catalysis. The enzyme requires a divalent metal ion, such as magnesium or manganese, for its activity.

Clinical Significance

Mutations in the gene encoding transaldolase have been associated with a rare genetic disorder known as transaldolase deficiency. This condition is characterized by impaired transaldolase activity, leading to a disruption in the PPP and subsequent metabolic abnormalities. Symptoms of transaldolase deficiency can vary widely and may include liver dysfunction, developmental delay, and neurological problems. Treatment options for this disorder are limited and mainly focus on managing the symptoms.

See Also

• Pentose phosphate pathway
• Ribose-5-phosphate
• NADPH