title: Substrate specificity of alpha-chymotrypsin-catalyzed esterification in organic media.
abstract: 11 amino acid derivatives were tested as alpha-chymotrypsin substrates in the esterification reaction with methanol in organic media. The reactions were carried out in water-saturated ethyl acetate and in acetonitrile containing 4% water. alpha-Chymotrypsin adsorbed on Celite was used as a catalyst. From initial reaction rate measurements, the Michaelis-Menten parameters Vmax and KM were determined. All the amino acid derivatives tested were esterified, and the highest values of kcat/KM were obtained with the N-acylated aromatic amino acids. Correlations between Michaelis-Menten parameters and physical properties of the substrates such as molar refractivity (MR) and log P were deduced. The results show that the specificity of the alpha-chymotrypsin towards the side chain of the amino acids in organic media is the same as that in aqueous media. However, the specificity towards the N-protecting group is opposite to that in water, so the reaction medium affects the interaction of this part of the molecule with the enzyme to a large extent.
authors.affiliation: Department of Biotechnology, University of Lund, Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Clapés
authors.forename: P
authors.initials: P
authors.lastname: Adlercreutz
mesh_terms: D000085:Acetates / Q000737:chemistry; D000097:Acetonitriles / Q000737:chemistry; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism*; D004952:Esters / Q000737:chemistry; D066298:In Vitro Techniques; D007700:Kinetics; D000432:Methanol; D012997:Solvents; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D014867:Water
chemical_list: D000085:Acetates; D000097:Acetonitriles; D000596:Amino Acids; D004952:Esters; D012997:Solvents; D014867:Water; C007650:ethyl acetate; D002918:Chymotrypsin; D000432:Methanol; C032159:acetonitrile