Electrochemical assay for 20S proteasome activity and inhibition with anti-cancer drugs

Publication date: Available online 12 February 2019

Source: Talanta

Author(s): Catarina Sofia Henriques de Jesus, Ana Maria Chiorcea-Paquim, Madalina Maria Barsan, Victor Constantin Diculescu

Abstract

The majority of eukaryotic regulated protein turnover is performed by the proteasome, a multi-catalytic enzyme. Due to the fact that proteasome enzyme abnormal functioning was observed in different malignant cells, the proteasome is becoming a target for medical treatment. In order to evaluate the mechanisms of action of pharmaceutical compounds on proteasome enzyme inhibition, detecting and characterizing its activity is essential. An electrochemical assay that allows the monitoring of the chymotrypsin-like activity and inhibition of the 20 S proteasome enzyme, based on the electrochemical detection of an electroactive compound released upon proteolysis of an adequate chymotrypsin-substrate is described. By employing differential pulse voltammetric measurement, the activity of the 20 S proteasome enzyme was investigated for different incubation times of 20 S with oligopeptide substrate as well as for different concentrations of substrate. Enzyme kinetic parameters were determined by voltammetry and the electrochemical assay compared with fluorescence spectroscopy. Electrochemical quartz crystal microbalance and atomic force microscopy were also used to investigate substrate interaction with the 20 S proteasome and their adsorption at the electrode surface. Finally, the new electrochemical assay allowed to investigate the mechanisms of two different proteasome inhibitor drugs, bortezomib and oprozomib, underlying the applicability of the assay for understanding proteasome inhibitor action.

Graphical abstract

Scheme of the 20S proteasome catalytic activity and principle of the electrochemical detection.

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