title: Papain hydrolysis of X-phenyl-N-methanesulfonyl glycinates: a quantitative structure-activity relationship and molecular graphics analysis.
abstract: The hydrolysis of 32 X-phenyl-N-methanesulfonyl glycinates by papain was investigated. It was found that the variation in the Michaelis constants could be rationalized by the following correlation equation: log 1/Km = 0.61 pi '3 + 0.46 MR4 + 0.55 sigma + 2.00 with a correlation coefficient of 0.945. In this expression, pi '3 is the hydrophobic constant for the more lipophilic of the two possible meta substituents, MR4 is the molar refractivity of 4-substituents, and sigma is the Hammett constant summed for all substituents. Using this equation, we designed, synthesized, and successfully predicted Km for a new congener intended to maximize binding (1/Km). The interactions involved in enzyme-substrate binding, as characterized by the correlation equation, are interpreted using a computer-constructed color three-dimensional-graphics molecular model of the enzyme active site. The nonenzymatic hydrolysis (both acid and basic) of phenyl hippurates yield rate constants which are well correlated by Hammett equations; however, log k for both acid and alkaline hydrolysis are not linearly related to log 1/Km or log kcat/Km.
mesh_terms: D001665:Binding Sites; D003201:Computers; D005998:Glycine / Q000031:analogs & derivatives* / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D010206:Papain / Q000378:metabolism*; D011485:Protein Binding; D013329:Structure-Activity Relationship; D013450:Sulfones / Q000378:metabolism*
chemical_list: D013450:Sulfones; D010206:Papain; D005998:Glycine