Steric Specificity in Synthesis of Heptuloses by Plants

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Abstract
The purpose of the study was to develop generalizations regarding the synthesis of hep-tuloses from other sugars when introduced into alfalfa leaves. After a 5-6-hour period any products present in leaf extracts were separated chromatographically and identified by various tests. Each of the 4 tetrose enantiomers induced an accumulation of a specific heptulose, each having the D-threo configuration at C-3, 4. In being converted the tetrose molecule appeared to remain intact since its configuration at C-2, 3 was preserved as C-5, 6 in the heptulose molecule which it induced. The suitability of hexuloses for heptulose biosynthesis in alfalfa leaves appears to be contingent upon their having the C-3, 4 configuration characteristic of transketolase substrates.