PREPARATION OF SUCROSE LABELED WITH Cl4 IN THE GLUCOSE OR FRUCTOSE COMPONENT* BY H. WOLOCHOW, E. W. PUTMAN, M. DOUDOROFF, W. Z. HASSID,

The problem of sucrose utilization has not been sufficiently studied to ascertain whether the disaccharide is used directly, inverted by hydrolysis, or broken down through some other mechanism prior to further metabolism. It is well known that fructose in its free form occurs as a relatively stable six-membered ring compound (pyranose configuration), whereas in the sucrose molecule it is found in the unstable five-membered ring form (furanose configuration), which cannot be isolated as a free substance. There is reason to suspect that this form, when liberated from sucrose by enzymatic action, might be metabolized in living cells in a different manner from the pyranose form or normal free fructose. The possibility also exists that the glucose half of the sucrose molecule, when first, liberated, is phosphorylated and also reacts differently from free glucose in living organisms. However, it is difficult to distinguish the breakdown products of sucrose from one another in their final utilization by ordinary methods. Labeling the components of sucrose with Cl4 affords a method for observing their metabolism in plants and animals. Since sucrose can be synthesized enzymatically from its constituent monosaccharides (1, 2), it is possible to label each half of the molecule by starting with monosaccharide units labeled with CY4. On the basis of earlier work the following reactions were postulated to account for the reversible phosphorolysis of sucrose with the enzyme from Pseudomonas saccharophila (2).