Trehalose 6-phosphate synthetase

Fig. 1.—Reactions Involved in the Metabolism of a,a-Trehalose. [Synthetase refers to the trehalose 6-phosphate synthetase (XDP-D-glucose D-glucose 6-phosphate l-n-glucosyl transferase), phosphatase to the trehalose 6-phosphate phosphatase, and phosphorylase to the a,a-trehalose phosphorylase.]...

Panek reported similar findings with extracts of bakers yeast, but detected trehalose, not trehalose 6-phosphate however, this may have been due to the presence of a highly active phosphatase. Elander studied the trehalose 6-phosphate synthetase of yeast after purifying the enzyme about 27-fold. The synthesis of trehalose 6-phosphate was inhibited by uridine 5 -pyrophosphate, which was competitive with UDP-D-glucose, and also by uridine 5 -triphosphate (UTP). It was also inhibited by 20 mM concentrations of inorganic phosphate, n-glucosyl phosphate, D-fructose 6-phosphate, o-mannose 6-phosphate, and trehalose 6-phosphate. n-Mannose 6-phosphate and trehalose 6-phosphate were competitive with n-glucose 6-phosphate. Free trehalose had no efiFect on the reaction. 

Schwoch studied the synthesis of trehalose in the crayfish, Orconectes limosus. Biosynthesis of the disaccharide could be detected in the abdominal muscle, antennal gland, hind-gut, integumentary tissue, and, to a lesser extent, in the stomach tissue. The trehalose 6-phosphate synthetase was soluble and was inhibited 50 by 80 milf trehalose. The rate of synthesis of trehalose was dependent on the season, and optimal activity in abdominal muscle occurred in February and March. The label from injected [ Cjtrehalose or D-[ C]glucose was foimd to be distributed from the hemolymph into organs much faster than the label from [ C]maltose. 

Newell and coworkers found that, during particular stages of fruit construction in Dictyostelium discoideum, four functionally related enzymes accumulated, reached characteristic levels of specific activity, and then disappeared partly or completely. These enzymes were UDP-d-glucose pyrophosphorylase, trehalose 6-phosphate synthetase, UDP-d-galactose 4-epimerase, and UDP-D-galactose polysaccharide n-galactosyl transferase. 

Killick and Wright examined the levels of the enzyme trehalose 6-phosphate synthetase at various stages of development of the slime mold, and obtained results that contradicted those of Both and Suss-man. They found that the enzyme was not only present at preculmination, but was also present in a masked form at the beginning of differentiation. By selective fractionation with ammonium sulfate and pre-incubation at 35°, they were able to unmask the enzyme and show its activity. Some evidence was obtained for the presence of an extracellular inhibitor of the enzyme. 

Gussin and McCormack presented evidence for the presence of trehalose 6-phosphate synthetase in the pollen of Lilium longiflorum. 

Trehalose phosphate is synthesized from G-6-P and UDPG by trehalose phosphate synthetase and converted to trehalose by a phosphatase. 

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