Synthesis in frozen-aqueous systems

S. Gerisch, G. Ullmann, K. Stubenrauch, and H.-D. Jakubke, Enzymatic peptide synthesis in frozen aqueous systems influence of modified reaction conditions on the peptide yield, Biol. Chem. Hoppe Seyler, 1994, 375, 825-828. 

M. Wagner, H. J. Hofmann, and H.-D. Jakubke, Influence of freeze-concentration effect on proteinase-catalysed peptide synthesis in frozen aqueous systems, Biochim. Biophys. Acta 1997, 1338, 253-258. 

Schuster M, Aaviksaar A, Haga M, Ullmann U, Jakubke HD. Protease-catalyzed peptide synthesis in frozen aqueous systems the freeze concentration model. Biomed Biochim Acta 1991 50 S84-S89. 

Enzymatic Peptide Synthesis in Frozen Aqueous Systems... 

Table 12.5-4. Comparative model peptide synthesis catalyzed by chymotrypsin in frozen aqueous systems and at room temperature.

Some new approaches to suppress competitive reactions in protease-catalyzed peptide synthesis have been developed in our group [14], namely leaving group manipulations at the acyl donor in kinetically controlled reactions, enzymatic synthesis in organic solvent-free microaqueous systems, cryoenzymatic peptide synthesis, and biotransformations in frozen aqueous systems using the reverse hydrolysis potential of proteases and other hydrolases... 

A step-by-step peptide synthesis from the N- to the C-terminus is not possible with chemical methods as it risks partial epimerization due to the repeated carboxy activation procedures, In constrast, the stereo- and regiospecificity of serine and cysteine proteases ensures integrity of the stereogenic center and allows ecological reaction conditions without side-chain protection. Scheme 4 shows the synthesis scheme using clostripain and chymo-trypsin as catalysts.The second coupling reaction was carried out by enzyme catalysis in a frozen aqueous system (see Section 4.2.3.1). 

---