Transaldolase is important for the balance of metabolites in the pentose-phosphate pathway. D-glyceraldehyde 3-phosphate + D-sedoheptulose 7-phosphate = beta-D-fructose 6-phosphate + D-erythrose 4-phosphate Carbohydrate degradation; pentose phosphate pathway; D-glyceraldehyde 3-phosphate and beta-D-fructose 6-phosphate from D-ribose 5-phosphate and D-xylulose 5-phosphate (non-oxidative stage): step 2/3. Belongs to the transaldolase family. Type 3B subfamily. Extended N-terminus.