The Major Secreted Cathepsin L1 Protease of the Liver Fluke,Fasciola hepatica
Journal of Biological Chemistry
A protease secreted by the parasitic helminth Fasciola hepatica, a 37-kDa procathepsin L1 (FheproCL1), autocatalytically processes and activates to its mature enzyme (FheCL1) over a wide pH range of 7.3 to 4.0, although activation is more rapid at low pH. Maturation initiates with cleavages of a small proportion of molecules within the central region of the prosegment, possibly by intramolecular events. However, activation to fully mature enzymes is achieved by a precise intermolecular cleavage
... at a Leu ؊12 -Ser ؊11 2His ؊10 sequence within the nonconserved C-terminal region of the prosegment. The importance of this cleavage site in enzyme activation was demonstrated using an active site variant FheproCL1Gly 26 (Cys 26 to Gly 26 ) and a double variant FheproCL1Pro ؊12 /Gly 26 (Leu ؊12 to Pro ؊12 ), and although both of these variants cannot autocatalytically process, the former is susceptible to trans-processing at a Leu ؊12 -Ser ؊11 2His ؊10 sequence by pre-activated FheCL1, but the latter is not. Another F. hepatica secreted protease FheCL2, which, unlike FheCL1, can readily accept proline in the S2 subsite of its active site, can trans-process the double variant FheproCL1Pro ؊12 /Gly 26 by cleavage at the Pro ؊12 -Ser ؊11 2His ؊10 sequence. Furthermore, the autoactivation of a variant enzyme with a single replacement, FheproCL1Pro ؊12 , was very slow but was increased 40-fold in the presence of FheCL2. These studies provide a molecular insight into the regulation of FheproCL1 autocatalysis. * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.