talb

TALB, or transaldolase B, is a bacterial enzyme that participates in the non-oxidative phase of the pentose phosphate pathway. It is commonly encoded by the talB gene and often coexists with talA (transaldolase A), providing metabolic flexibility in pentose and hexose phosphate interconversion.

Functionally, TALB catalyzes a reversible transfer of a three-carbon dihydroxyacetone unit from sedoheptulose-7-phosphate to glyceraldehyde-3-phosphate, yielding erythrose-4-phosphate and fructose-6-phosphate. This reaction helps balance carbon flux between the pentose phosphate pathway and glycolysis, contributing to the cellular pools of sugar phosphates needed for biosynthesis and energy production.

Mechanistically, TALB belongs to class I transaldolases and employs a catalytic lysine to form a Schiff base with a substrate. Through this intermediate, a three-carbon unit is transferred between sugar phosphates before the products are released.

Genetically, talB is found across many bacteria, including Escherichia coli and Salmonella species. In some organisms, talB can partially compensate for talA under certain conditions, supporting redundancy in the transaldolase repertoire and enabling flexible responses to environmental changes.

Structure and evolution-wise, TALB enzymes share a conserved fold typical of class I transaldolases, often described as TIM-barrel-like, and exhibit sequence diversity that reflects adaptation to different ecological niches while preserving core catalytic residues.

Applications and relevance include the study of PPP flux in metabolic engineering, where manipulating TALB activity can influence production of nucleotides, sugar derivatives, or biofuels. TALB is also considered in research on antimicrobial targets due to its role in central carbon metabolism.