Transaldolaasi

Transaldolase is an enzyme that catalyzes the reversible transfer of a dihydroxyacetone group from a ketose donor to an aldose acceptor. It is a key enzyme in the pentose phosphate pathway, a metabolic pathway parallel to glycolysis. In this pathway, transaldolase, along with transketolase, facilitates the interconversion of sugars with different carbon chain lengths. Specifically, transaldolase catalyzes the reaction between fructose-6-phosphate and glyceraldehyde-3-phosphate to produce erythrose-4-phosphate and sedoheptulose-7-phosphate. This process is crucial for the production of nucleotides and reducing equivalents like NADPH.

The enzyme functions by forming a Schiff base intermediate with the donor sugar, fructose-6-phosphate. This intermediate then undergoes cleavage, releasing the aldose acceptor, glyceraldehyde-3-phosphate, and the dihydroxyacetone moiety bound to the enzyme. This moiety is then transferred to the acceptor sugar. Transaldolase is a dimeric enzyme and utilizes a lysine residue in its active site to form the Schiff base.

Mutations in the gene encoding transaldolase can lead to a rare metabolic disorder known as transaldolase deficiency. This deficiency can cause severe neurological problems, including intellectual disability and seizures, due to the impaired functioning of the pentose phosphate pathway. The pathway's role in providing NADPH for reductive biosynthesis and protecting cells from oxidative stress is critical for brain development and function. Research continues to explore the precise mechanisms of transaldolase action and the full spectrum of consequences arising from its deficiency.