Purification and partial characterization of kininogenase activity from Schistosoma mansoni adult worms

Abstract

An enzyme presenting kallikrein-like activity (designated sK1) was purified from the supernatant of Schistosoma mansoni adult worm homogenate. The enzyme cleaves bradykinin from purified rat plasma kininogen. Activity was optimal at pH 9.0 and the enzyme showed amidolytic activity, since it hydrolysed the kallikrein synthetic substrate D-Pro-Phe-Arg-p-nitroanilide. The activity of sK1 upon rat plasma kininogen was strongly inhibited by the serine proteinase inhibitors phenylmethanesulfonyl fluoride, aprotinin or soybean trypsin inhibitor, but not by ethylenediaminetetraacetic acid or sodium tetrathionate. The molecular mass of sK1, as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, was 66 kDa and the pI value, estimated by analytical chromatofocusing, was 4.2. Physical and chemical properties suggest that sK1 is a serine proteinase of the kallikrein family. Evidence is presented which suggests that sK1 is a component of the tegumental surface of the parasite and the levels of its activity in the male adult worm are approximately 21 times higher than those in the female adult worm. The intravenous injection of 3 micrograms of sK1 into an anaesthetized rat induced a drastic reduction in the arterial blood pressure of the animal. This effect lasted for about 1 min, and was followed by a progressive recovery of the arterial pressure. Neither bradycardia nor cardiac arrhythmias were noticed, suggesting a peripheral vasodilation effect. The presence of sK1 on the surface of adult male worms could play an important role in the wandering capacity of coupled worms into the visceral vasculature of the host.

Cysteine proteases of human hookwormNecator Americanus as virulencefactors and implications for drug design with anti-heparin and heparin analogs: A bioinformatics study

“…The docking studies are speculative of NA CPs' heparin-assisted HMWK-cleaving activity. Such assistance by heparin, already verified for the proteases from other parasites viz: T.Cruzi [40] [41] and S.mansoni [52] that navigate blood capillaries points to similar survival strategy adoption by larvae-stage NA, which traverses blood capillaries. This study is an attempt to provide molecular level information based on computational predictions, decoding previously unreported functions of the individual NA cysteine proteases and the role heparin could be playing.…”

“…Emulation of plasma kallikrein activity has been reported for cruzain [40] [41] -a cysteine protease from T.Cruzi that traverses blood capillary vessels. Such function has been suggested also for SmSP1 [51] -serine protease of blood fluke S.mansoni, as kallikrein-like activity had been reported for a serine protease from S.mansoni [52] [53] . The blood stream navigating physiology of the mentioned pathogens perhaps explains their need for cleaving HMWK to generate bradykinin for vasodilation and blood clot prevention.…”

Schistosoma mansoni infection enhances host portal vein contraction: role of potassium channels and p38 MAP kinase

“…A kallikrein-like activity was previously reported in the homogenate of S. mansoni, which would be implicated in the vasodilation of host mesenteric venules due to the production of bradykinin [27]. Bradykinin is an endogenous vasodilator nonapeptide, that in mice portal vein mediates vasodilation through the release of nitric oxide from endothelial cells [28].…”

The impact of schistosomes and schistosomiasis on murine blood coagulation and fibrinolysis as determined by thromboelastography (TEG)

“…Other proposed methods of schistosome-induced dampening of coagulation include the action of a parasite kallikrein-like enzyme which may cleave the plasma protein kininogen to generate the small vasoactive peptide bradykinin [31]. Bradykinin can trigger the release of the platelet degranulation inhibitor prostacyclin (PGI 2 ) from endothelial cells [32].…”