title: Combinatorial formulation of biocatalyst preparations for increased activity in organic solvents: salt activation of penicillin amidase.
abstract: A combinatorial experimental technique was used to identify salts and salt mixtures capable of activating penicillin amidase in organic solvents for the transesterification of phenoxyacetate methyl ester with 1-propanol. Penicillin amidase was lyophilized in the presence of various chloride and acetate salts within 96-deep-well plates and catalytic rates measured to determine lead candidates for highly salt-activated preparations. The kinetics of the most active formulations were then further evaluated. These studies revealed that a formulation consisting of 98% (w/w) of a 1:1 KAc:CsCl salt mixture, 1% (w/w) enzyme, and 1% (w/w) potassium phosphate buffer was approximately 35,000-fold more active than the salt-free formulation in hexane, as reflected in values of V(max)/K(m). This extraordinary activation could be extended to more polar solvents, including tert-amyl alcohol, and to formulations with lower total salt contents. A correlation was found between the kosmotropic/chaotropic behavior of the salts (as measured by the Jones-Dole B coefficients) and the observed activation. Strongly chaotropic cations combined with strongly kosmotropic anions yielded the greatest activation, and this is likely due to the influence of the ions on protein-water and protein-salt interactions.
authors.affiliation: Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Lindsay
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Clark
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Dordick
mesh_terms: D000433:1-Propanol / Q000737:chemistry*; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D004789:Enzyme Activation; D005240:Feasibility Studies; D007700:Kinetics; D009930:Organic Chemicals / Q000737:chemistry; D010399:Penicillin Amidase / Q000737:chemistry*; D010642:Phenoxyacetates / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D009930:Organic Chemicals; D010642:Phenoxyacetates; D012492:Salts; D012997:Solvents; D000433:1-Propanol; D010399:Penicillin Amidase