Mechanism of action of transaldolase. I. Crystalization and properties of yeast enzyme.

The transformation of pentose to hexoses was first observed by Dische (1) in hemolysates of red blood cells. Glucose 6-phosphate was shown to accumulate when ribose S-phosphate was incubated in a crude enzyme preparation from liver (2), and fructose 6-phosphate was identified by Clock (3) as the first product of the pentose-hexose transformation. It was shown by de la Haba and Racker (4) that this transformation requires transketolase and a second enzyme obtained from yeast. This enzyme was shown by Horecker and Smyrniotis (5) to act as a transaldolase that transfers the dihydroxyacetone moiety of sedoheptulose 7-phosphate to glyceraldehyde 3-phosphate to form fructose 6-phosphate. The distribution and biological functions of transaldolase have been reviewed elsewhere (6). The enzyme has been partially purified from spinach and various types of yeast (7-Q). This paper deals with the purification and crystallization of transaldolase from bakers’ yeast, and with studies of some of its properties.