Cyantraniliprole as papain inhibitor and its action in molecular docking studies

Abstract

Importance of the work: Biosensors have emerged as an alternative method for the determination of cyantraniliprole; however, they still require expensive enzymes.
Objectives: A papain assay was applied as a model for the study of inhibition by cyantraniliprole.
Materials & Methods: Papain, an inexpensive enzyme found mainly in papaya resin, belongs to a proteolytic enzyme group capable of digesting large proteins into their smaller constituents. Papain activity was determined using a colorimetric reaction. N-benzoyl-L-arginine-p-nitroanilide (BAPNA) was hydrolyzed to a yellow product, p-nitroaniline, which could be monitored spectrophotometrically at 430 nm.
Results: The enzyme was optimally active at pH 7. The Michaelis constant of papain toward this substrate was 2.40 mM and the kinetic constant Vmax was 0.0169 μmol/min. This assay was investigated using the organic solvents dimethyl sulfoxide (DMSO) and acetonitrile. The enzyme activities were very similar when working in either phosphate buffer or phosphate buffer containing 3% (volume per volume, v/v) acetonitrile or 10% (v/v) DMSO. Then, the optimum conditions were applied to the quantitative analysis of cyantraniliprole. The activity of papain was strongly inhibited by cyantraniliprole. The preliminary results showed a wide linear range from 4.5 to 47.0 parts per million. The molecular docking studies confirmed that cyantraniliprole interacted with papain similarly to BAPNA, with the limit of detection being in the low parts per million.
Main finding: The work represents the first investigation of papain inhibition by cyantraniliprole. With its simplicity and low cost, this assay has high potential for use in the field.