Physicochemical characterization of an aspin (rBm-33) from a filarial parasite Brugia malayi against the important human aspartic proteases

Abstract

The aspartic protease inhibitory efficiency of rBm-33, an aspin from a filarial parasite Brugia malayi was investigated. rBm-33 was found to be thermostable up to 90°C and it forms a stable ‘enzyme-product’ complex with human pepsin. Aspartic protease inhibitory activity was investigated using UV spectroscopy and isothermal titration calorimetry. Our results suggest that rBm-33 inhibits the activity of important human aspartic proteases that were examined with binding constants (K_b) values between 10.23 × 10³ and 6.52 × 10³ M⁻¹. The binding reactions were enthalpy driven with ΔH_b values between −50.99 and −46.07 kJ mol⁻¹. From kinetic studies, pepsin inhibition by rBm-33 was found to be linear competitive with an inhibition constant (Ki) of 2.5 (±0.8) nM. Because of the inhibitory efficacy of Bm-33 against important human aspartic proteases which play a vital role in immune-regulation along with other functions, Bm-33 can be projected as a drug target for the filariasis.

Keywords::

• Filariasis
• Brugia malayi
• competitive inhibition
• thermal stability
• aspartic proteases
• drug target

Acknowledgements

The authors wish to thank Dr. Sadasivan at Kannur University, Kerala, India for allowing us to carry out the isothermal titration calorimetric experiments.

Declaration of interest

NRSK and SSR thank University Grants Commission, India. RBN thanks CSIR, India, for financial assistance. The authors report no conflict of interest.