title: The major secreted cathepsin L1 protease of the liver fluke, Fasciola hepatica: a Leu-12 to Pro-12 replacement in the nonconserved C-terminal region of the prosegment prevents complete enzyme autoactivation and allows definition of the molecular events in prosegment removal.
abstract: 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 downward arrowHis-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 FheproCL1Gly26 (Cys26 to Gly26) and a double variant FheproCL1Pro-12/Gly26 (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 downward arrowHis-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/Gly26 by cleavage at the Pro-12-Ser-11 downward arrowHis-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.
authors.affiliation: Institute for the Biotechnology of Infectious Diseases, University of Technology Sydney, Building 4, Harris Street, Ultimo, Sydney, New South Wales 2007, Australia.
authors.forename: Colin M
authors.initials: CM
authors.lastname: Stack
authors.forename: Sheila
authors.initials: S
authors.lastname: Donnelly
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lowther
authors.forename: Weibo
authors.initials: W
authors.lastname: Xu
authors.forename: Peter R
authors.initials: PR
authors.lastname: Collins
authors.forename: Linda S
authors.initials: LS
authors.lastname: Brinen
authors.forename: John P
authors.initials: JP
authors.lastname: Dalton
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002384:Catalysis; D002403:Cathepsins / Q000737:chemistry* / Q000235:genetics; D004013:Dicrocoelium / Q000201:enzymology*; D004789:Enzyme Activation / Q000235:genetics; D004792:Enzyme Precursors / Q000737:chemistry* / Q000235:genetics; D015801:Helminth Proteins / Q000737:chemistry* / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007930:Leucine / Q000737:chemistry / Q000235:genetics; D020125:Mutation, Missense; D011392:Proline / Q000737:chemistry / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000235:genetics
chemical_list: D004792:Enzyme Precursors; D015801:Helminth Proteins; D011392:Proline; D002403:Cathepsins; C509464:cathepsin L1, Fasciola hepatica; D007930:Leucine