Mechanism of action of transketolase. I. Properties of the crystalline yeast enzyme.

For detailed studies on the mode of action of an enzyme a readily available source and a convenient method of preparation are of distinct advantage. Accessible sources such as bakers’ yeast (1) and spinach leaves (2) have, therefore, been used for large-scale preparations of transketolase in spite of the fact that extracts of Escherichia coli, in which the cleavage of ribose-5-P to triose-P was first observed (3), or To&a yeast (4) are 3 to 5 times as active. With the development of cellulose derivatives for protein fractionation (5), the procurement of transketolase in sufficient quantities (4) for isolation of enzyme-substrate intermediates has become feasible (6, 7). It is the purpose of this paper to report on properties of the crystalline yeast enzyme that have not been recorded previously.