Abstract

The enzyme 3-hydroxykynurenine transaminase (HKT) acts as an important enzyme in tryptophan catabolism of disease-carrier insects, e.g. Aedes aegypti and Anopheles gambiae. HKT is a detoxification enzyme that converts 3-hydroxykynurenine (a precursor for reactive nitrogen and oxygen species) into xanthurenic acid (stable and nontoxic compound). We have previously synthesized eleven new oxadiazole derivatives and demonstrated their noncompetitive inhibitory activity towards HKT from A. aegypti (https://doi.org/10.1016/j.bmc.2019.115252). These findings are presented in a research paper accompanying the present technical report on a new assay to overcome the fact that the substrate and product of the HKT-catalyzed reaction exhibit maximum absorption at very near wavelength (370 and 369 nm, respectively). The methods previously described in the literature rely on chromatographic separation prior to absorbance quantification, which limits their use for inhibitor screening. Due to HKT attractive features as a molecular target for larvicidal compounds, we report herein a new, faster and affordable methodology to evaluate the enzymatic activity of recombinant HKT, and therefore allow for the fast screening of potential HKT inhibitors via absorbance spectrophotometer. The advantages of the proposed methodology to previously described ones are:•It is faster and cheaper than HPLC-based assays because it does not require the use of chromatography columns and solvents to separate reaction components;•It uses of 96-well plates, enabling the simultaneous quantification of samples;•It can be applied to all transaminases that have xanthurenic acid as a product.

Highlights

  • The search for new chemical insecticides has gained importance in recent years due to the growing outbreaks of arboviruses (Yellow Fever, Dengue, Zika and Chikungunya Fever) and the regular frequency of the occurrence of malaria in tropical regions [1]

  • Due to hydroxykynurenine transaminase (HKT) attractive features as a molecular target for larvicidal compounds, we report a new, faster and affordable methodology to evaluate the enzymatic activity of recombinant HKT, and allow for the fast screening of potential HKT inhibitors via absorbance spectrophotometer

  • We describe the standardization of an absorbance-based biochemical protocol to evaluate HKT activity by means of xanthurenic acid (XA)

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Summary

Method Article

These findings are presented in a research paper accompanying the present technical report on a new assay to overcome the fact that the substrate and product of the HKT-catalyzed reaction exhibit maximum absorption at very near wavelength (370 and 369 nm, respectively). Method name: Detection of xanthurenic acid − Fe3+ complex in enzymatic assay. Evaluation of HKT activity from Aedes aegypti and Anopheles gambiae via HPLC-UV and LC-MS/MS methods [3] Q. Del Grosso, Study of Anopheles gambiae 3-hydroxykynurenine transaminase activity and inhibition by LC-MS/MS method, J.

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