title: The heavy-light chain loop of human cathepsin-L modulates its activity and stability.
abstract: Differences evident in the sequence alignment of human cathepsin-L with shrimp cathepsin-L and silicatein-alpha suggest the indirect involvement of the heavy to light chain loop (E 286 to E 289) in the function of these enzymes. Deletion of the loop and adjacent residues S 290 to N 293, decreased specific protease activity by 81% and 63%, respectively; complete substitution for the corresponding silicatein-alpha loop decreased activity by 35%. In all cases the Km was largely unchanged. The conformational stability of human procathepsin-L was not altered by deletion of E 286 to E 289 but increased on deletion of S 290 to N 293. Therefore, shortening the loop does not change substrate affinity but does influence activity, in part via conformational change.
authors.affiliation: Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Fairhead
authors.forename: Christopher F
authors.initials: CF
authors.lastname: van der Walle
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D056668:Cathepsin L; D002403:Cathepsins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004795:Enzyme Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000378:metabolism; D033542:Pandalidae / Q000201:enzymology; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D050505:Mutant Proteins; C112571:silicatein alpha; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L