Proteases catalyzed condensation study

Protease-Catalyzed Condensation Study. Based on the exceptional activity of trypsin and a-chymotrypsin from bovine pancreas (Table I), protease enzymes were identified as target catalysts. Consequently, a series of proteases (i.e. serine, cysteine, aspartic, and metallo) were selected in order to screen their ability to catalyze siloxane condensation with trimethylsilanol. The reactions... 

Figure 2. Protease-catalyzed condensation study of trimethylsilanol after three hours.

In the first report on (isolated) enzymatic catalysis in an IL, Erbeldinger and co-workers described the thermolysin-catalyzed synthesis of Z-aspartame in [BMIM][PF ] [17]. By condensation of Z-Asp-OH and H-Phe-OMe, the sweetener could be prepared in 95% yield, which is similar to the yield that has been obtained in traditional organic solvents [Eq. (4)]. A 5% water content was found critical for the enzymatic activity. Moreover, removal of the water by vacuum resulted in easy isolation of the product by precipitation [17]. Further, in another application of a protease, Adler-creutz and co-workers used a-chymotrypsin to study transesterification of Ac-Phe-OEt with 1-butanol [34] [Eq. (5)]. They found that at low water activity (a ), the... 

Followed by these observations, Bassindale et al. [ 19,20] studied the use of various homologous lipase and protease enzymes to catalyze the formation of molecules with a single siloxane bond during the in vitro hydrolysis and condensation of alkoxysilanes under mild reaction conditions. They found that non-specific interactions with trypsin promoted the hydrolysis of alkoxysilanes, while the active site was determined to selectively catalyze the condensation of silan-ols. One interesting observation was that when trypsin from various sources was employed different extents of conversion were observed. Comparatively, the activity of trypsin from a bovine pancreas was greater than the alternate sources of trypsin. Although various sources (e.g., mammalian, fish) of trypsin are similar (e.g., tertiary structure), their selectivity and activity was found to be different due to different optimum pH ranges and/or levels of calcium (an additive). 

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