Identification, purification, and characterization of a secretory serine protease in an Indian strain of Leishmania donovani

Abstract

An aprotinin sensitive serine protease was identified in the culture supernatant of the Indian strain of Leishmania donovani (MHOM/IN/1983/ AG83). The protease was subsequently purified and characterized. The apparent molecular mass of the enzyme was 115 kDa in SDS-PAGE under non-reducing condition, while on reduction it showed a 56 kDa protein band indicating that the protease is a dimeric protein. The purified enzyme was optimally active at the pH and temperature of 7.5 and 28°C, respectively. Assays of thermal stability indicated that the enzyme preserved 59% of activity even after pretreatment at 42°C for 1 h. The purified protease was not glycosylated and its isoelectric pI was 5.0. N-α-p-tosyl-L-arginine methylester (TAME) appeared to be relatively better substrate among the commonly used synthetic substrates. The enzyme was inhibited by Ca2+ and Mn2+, but activated by Zn2+. The protease could play important role(s) in the pathogenesis of visceral leishmaniasis or kala-azar. © Springer Science+Business Media, LLC. 2008.