Most probably the N-terminal region of the metalloproteinase domain of native moojenin under non-reducing conditions cannot be determined by Edman degradation because it is blocked by the presence of pyroglutamic acid, as is usually observed for other SVMPs of the PIII subclass (Muniz et al., find more 2008). The proteolytic fragment was present in a low proportion compared to the unprocessed moojenin; however, it could be detected by sequenator analysis since this procedure presents higher sensitivity than SDS-PAGE. The proteolytic activity of the moojenin was assayed on bovine fibrinogen. Moojenin degraded fibrinogen, as evidenced by the appearance of new protein bands at the bottom of the gel. Apparently,
moojenin completely degraded the Aα-chain and Bβ-chain of fibrinogen, in a time-dependent manner ( Fig. 3A). The Aα-chain was totally degraded even at the shortest time tested (15 min), while the Bβ-chain was degraded at the longest time (90 min). The γ-chain appeared
unaffected throughout the incubation period examined. The optimal temperature range for the degradation of the fibrinogen chains was determined to be 30–40 °C. Activity was completely lost at temperatures ≥50 °C ( Fig. 3C). buy GSK J4 The digestion pattern of the moojenin was similar to other purified metalloproteinases from bothropic venom, for example, BleucMP from Bothrops leucurus ( Gomes et al., 2011), BlaH1 from Bothrops lanceolatus (Fer-de-lance) ( Stroka et al., 2005) and BmooMPα-I from B. moojeni ( Bernardes et al., 2008). All these enzymes are classified as α-fibrinogenases. They degrade the Aα-chain of fibrinogen first, followed by the Bβ-chain, and show no effect on the γ-chain. SVMPs are usually more active at pHs ranging from neutral to basic (Manning, 1995;
Xu et al., 2004). Interestingly, for the first time, we demonstrated the action of a proteinase at acidic pH. Moojenin degraded fibrinogen chains at pH 4, but not at pHs ranging from neutral to basic (Fig. 3B). Chelating agents such as EDTA, 1,10 phenanthroline and β-mercaptoethanol inhibited the fibrinogenolytic Immune system activity of the enzyme. In contrast, benzamidine, leupeptin and PMSF did not affect this activity (Fig. 3D). These results suggest that moojenin belongs to the class of metalloproteinases and disulfide bonds are important for the maintenance of its structure. Numerous snake venom proteinases have been isolated and characterized (Serrano and Maroun, 2005). These enzymes affect, for example, fibrinogenolysis, platelet aggregation, the complement system, blood pressure and blood coagulation (Markland, 1998; Zhang et al., 1998; Castro et al., 2004; Kini, 2005; Serrano and Maroun, 2005). Interestingly, moojenin presented a coagulant activity. These results are in accordance with the finding of Serrano and colleagues (Serrano et al., 1993b). These authors purified a metalloproteinase, denominated MPB, with a residual coagulant activity.