The transesterification activity of Bioprase, a protease from Bacillus subtilis, in dimethylformamide (DMF) is found to depend strongly on water addition. For the transesterification between thymidine and divinyl adipate by Bioprase in DMF with water (5–40%), the conversion rate of thymidine to the ester is much higher than the rate in DMF without the addition of water. For example, the transesterification reaction of 0.25 M thymidine with 1 M divinyl adipate in DMF in the presence of 10% water was catalyzed by Bioprase (50 mg · ml?1) at 30 °C for only 10–20 minutes to give 5′‐O‐vinyladipoyl thymidine (conversion ca. 90%), but the reaction did not proceed without the addition of water. Furthermore, the water effect is useful for the transesterification of thymidine with divinyl sebacate, which has a longer alkyl chain than divinyl adipate. This investigation showed that DMF adsorbs on the enzyme surface instead of essential water in the reaction of DMF without addition of water. On the other hand, in the reaction of DMF/water cosolvents, essential water bound to enzyme was not removed by DMF, and a higher transesterification activity occurs thereafter.
Effect of water on the transesterification of thymidine catalyzed by Bioprase in DMF.
