Abstract: Arylacylamidase can be stabilized by inhibiting conformational changes using either o-cresol or benzoic acid or salts of benzoic acid as a stabilizing agent. The compositions show significantly enhanced stability of arylacylamidase in aqueous solution, lyophilized, and solid-phase formats.

Abstract: A method and unitized test composition is described for the estimation of an anilide in which the enzymatic hydrolysis of the anilide and colorimetric quantitation of aniline or aniline derivative can be done simultaneously.The hydrolysis of the anilide is catalyzed by a known enzyme, arylacylamidase, E. C. 3.5.1.13. Stabilization of the enzyme is provided by the addition of controlled amounts of a compound containing alcoholic and/or aromatic groups such as ortho-cresol, isopropanol or benzoate.Basically, the unitized test composition comprises (i) arylacylamidase, (ii) a controlled amount of an organic compound containing alcoholic and/or aromatic groups which acts as both a stabilizer for the arylacylamidase and forms a colored product with aniline, and (iii) a novel oxidant/catalytic agent for accelerating color development.The benefit of such methodology results in a one step addition of the complete reagent to the sample, serum or matrix containing the anilide as opposed to a several step addition.