Enzymatic Reactions in Aqueous-Organic Media. II. Effects of Reaction Conditions and Selectivity in the Esterification of Aromatic Amino Acids by α-Chymotrypsin in Alcohols

N-Acetylated aromatic amino acids were esterified by α-chymotrypsin suspended in alcohols. The reaction rate and the yields of the esters depended primarily on the amount of the aqueous buffer solution in which α-chymotrypsin was dissolved. The reaction rate increased but the equilibrium yield of the esters decreased with increasing concentration of water. High substrate selectivity and stereospecificity were observed for l-aromatic amino acids; and therefore, in this system α-chymotrypsin was considered to be an effective catalyst which maintains its native conformation. When the amount of the substrate was increased, the present reactions gave higher yields of the esters than the reactions in chloroform (two-phase method).