Physicochemical properties of IgA protease from Haemophilus influenzae ATCC49247 and its decomposition of IgA1 with low glycosylation

Abstract:

[Background] Recently, IgA proteases that specifically cleave human IgA1 molecules have been considered as potential drugs for the treatment of IgA nephropathy (IgAN), but its biological activity may be affected by various physical and chemical factors. [Objective] To explore the physicochemical properties of Haemophilus influenzae ATCC49247 IgA protease for determining the optimal conditions and then to observe its decomposition of low glycosylated IgA1. [Methods] IgA protease was isolated and purified from the bacterial culture solution and the hydrolysis activity of IgA protease and its decomposition of low glycosylated IgA1 were detected by SDS-PAGE electrophoresis under various physicochemical conditions. [Results] H. influenzae ATCC49247 IgA protease tolerated a wide range of temperatures and the optimum temperature is 50 °C. IgA protease irreversibly lost stability above 60 °C. IgA protease maintained full catalytic activity between pH 6.0 and 9.0. PMSF of 1 mmol/L and SDS of above 10 mmol/L strongly inhibited the activity of IgA protease, whereas DTT and EDTA had no significant effect on its activity. IgA protease was obviously inhibited by all concentrations of Al3+, Fe3+ and high concentration of Cu2+, Zn2+ and Fe2+, whereas Co2+, Mn2+, Ca2+, Ni2+ and Mg2+ had no significant effect on its activity. By selecting the most suitable conditions for IgA protease, we found that most of the low-glycosylated IgA1 substrate could be degraded by IgA protease. [Conclusion] IgA protease can maintain good enzyme activity under the optimal conditions, when exerting the degradation of low glycosylated IgA1 and the result lays the fundation for the clinical research and the further development of the medicinal value for IgA protease.