Apart from catalyzing the common two-substrate reaction with ketose as donor substrate and aldose as acceptor substrate, transketolase is also able to catalyze a one-substrate reaction utilizing only ketose (xylulose B-phosphate) as substrate. The products of this one-substrate reaction were glyceraldehyde 3-phosphate and erythrulose. No free glycolaldehyde (a product of xylulose B-phosphate splitting in the transketolase reaction) was revealed,