title: Identification and characterization of 3-substituted pyrazolyl esters as alternate substrates for cathepsin B: the confounding effects of DTT and cysteine in biological assays.
abstract: Substituted pyrazole esters were identified as hits in a high throughput screen (HTS) of the NIH Molecular Libraries Small Molecule Repository (MLSMR) to identify inhibitors of the enzyme cathepsin B. Members of this class, along with functional group analogs, were synthesized in an effort to define the structural requirements for activity. Analog characterization was hampered by the need to include a reducing agent such as dithiothreitol (DTT) or cysteine in the assay, highlighting the caution required in interpreting biological data gathered in the presence of such nucleophiles. Despite the confounding effects of DTT and cysteine, our studies demonstrate that the pyrazole 1 acts as alternate substrate for cathepsin B, rather than as an inhibitor.
authors.affiliation: Penn Center for Molecular Discovery, University of Pennsylvania, 1024 Vagelos Research Laboratories, Philadelphia, PA 19104-6383, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Myers
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Napper
authors.forename: Nuzhat
authors.initials: N
authors.lastname: Motlekar
authors.forename: Parag P
authors.initials: PP
authors.lastname: Shah
authors.forename: Chun-Hao
authors.initials: CH
authors.lastname: Chiu
authors.forename: Mary Pat
authors.initials: MP
authors.lastname: Beavers
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
authors.forename: Donna M
authors.initials: DM
authors.lastname: Huryn
authors.forename: Amos B
authors.initials: AB
authors.lastname: Smith
mesh_terms: D001681:Biological Assay / Q000379:methods; D002244:Carbon / Q000737:chemistry; D002401:Cathepsin B / Q000737:chemistry* / Q000378:metabolism; D002626:Chemistry, Pharmaceutical / Q000379:methods; D003545:Cysteine / Q000494:pharmacology*; D004229:Dithiothreitol / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015195:Drug Design; D004952:Esters / Q000737:chemistry*; D006801:Humans; D020128:Inhibitory Concentration 50; D008956:Models, Chemical; D011485:Protein Binding; D019163:Reducing Agents / Q000494:pharmacology; D013997:Time Factors
chemical_list: D004952:Esters; D019163:Reducing Agents; D002244:Carbon; D002401:Cathepsin B; D003545:Cysteine; D004229:Dithiothreitol