The characterization and stereochemical utilization of phosphorothioates produced by chemical and enzymatic synthesis
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Sucrose synthetase (UDP-glucose-fructose glycosyl transferase, E. C. 2. 4. 1. 13) catalyzes the production of uridine diphosphoglucose and fructose from uridine diphosphate and sucrose, An overall stereochemical course for this enzyme has not been established for the P phosphorus of its substrate uridine diphosphoglucose (UDPglucose). This thesis presents a method for the determination of this stereochemical course through the use of phosphorothioates. The phosphorothioate analogues of glucose-1-phosphate and uridine diphospho-glucose (UDP-glucose P(S) or UDP-P(S) glucose) were synthesized, purified, and characterized by P NMR and by HPLC. In 31 addition, the overall relative rate kinetics of these phosphorothioates are compared to the natural oxygen analogue for each enzyme studied. Uridine diphosphoglucose-P(S) obtained from uridine diphosphoglucose pyrophosphorylase (E. C. 2. 4. 2. 9) is not a kinetically competent substrate for sucrose synthetase. An attempt to synthesize, specify the opposite isomer by using a combination of galactose-1-phosphate uridylyl transferase (E. C. 2. 7. 12) and phosphoglucomutase (E. C. 2. 7. 5. 1) with glucose-1-phosphorothioate only produced the identical isomer as determined by high field NMR. Attempts were also made to produce thiocarbamoyl phosphate, carbamoyl phosphorothioate, and thiocitrulline for possible investigation as substrates of enzymes of the urea cycle (carbamoyl phosphate synthetase E. C. 2. 7. 2. 5, ornithine transcarbamoylase E. C. 2. 1. 3. 3, and arginosuccinate synthetase E. C. 6. 3. 4. 5).
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Bibliography: leaves 71-72.
Newborn, Joey Scott (1987). The characterization and stereochemical utilization of phosphorothioates produced by chemical and enzymatic synthesis. Master's thesis, Texas A&M University. Available electronically from