The use of proteinases for the synthesis of peptides and esters has been studied for over 50 years and has increased substantially over recent years. In particular, the use of proteinases in anhydrous organic solvents ( < 0.01% water), where they exhibit novel properties, is gaining momentum.¹ However, most of the work on peptide synthesis has been on the use of proteinases in water-miscible solvents. There are a number of advantages in employing water-miscible solvents.² For example, some amino acid derivatives are poorly soluble in nonpolar solvents and limitations due to the diffusion of substrates in biphasic systems or enzymes suspended in hydrophobic solvents are avoided. The main disadvantage of employing water-miscible solvents is that at high concentrations, many enzymes are relatively inactive or denatured due to the stripping of enzyme-bound water.³ The use of proteinases isolated from extreme thermophiles, with their inherent stability to extremes of pH and temperature and to organic solvents, would seem to be one of the obvious ways of solving these problems. In addition, the reactions could be carried out at higher temperatures, which would result in benefits from increased substrate solubilities, accelerated rates of diffusion, and decreased viscosity.