Kinetic characterization and molecular docking of a novel, potent, and selective slow-binding inhibitor of human cathepsin L.
A novel small molecule thiocarbazate (PubChem SID 26681509), a potent inhibitor of human cathepsin L (EC 3.4.22.15) with an IC(50) of 56 nM, was developed after a 57,821-compound screen of the National Institutes of Health Molecular Libraries Small Molecule Repository. After a 4-h preincubation with cathepsin L, this compound became even more potent, demonstrating an IC(50) of 1.0 nM. The thiocarbazate was determined to be a slow-binding and slowly reversible competitive inhibitor. Through a transient kinetic analysis for single-step reversibility, inhibition rate constants were k(on) = 24,000 M(-1)s(-1) and k(off) = 2.2 x 10(-5) s(-1) (K(i) = 0.89 nM). Molecular docking studies were undertaken using the experimentally derived X-ray crystal structure of papain/CLIK-148 (1cvz. pdb). These studies revealed critical hydrogen bonding patterns of the thiocarbazate with key active site residues in papain. The thiocarbazate displayed 7- to 151-fold greater selectivity toward cathepsin L than papain and cathepsins B, K, V, and S with no activity against cathepsin G. The inhibitor demonstrated a lack of toxicity in human aortic endothelial cells and zebrafish. In addition, the thiocarbazate inhibited in vitro propagation of malaria parasite Plasmodium falciparum with an IC(50) of 15.4 microM and inhibited Leishmania major with an IC(50) of 12.5 microM.
Shah
Parag P
PP
Penn Center for Molecular Discovery, University of Pennsylvania, 1024 Vagelos Laboratories, Philadelphia, PA 19104-6383, USA.
Myers
Michael C
MC
Beavers
Mary Pat
MP
Purvis
Jeremy E
JE
Jing
Huiyan
H
Grieser
Heather J
HJ
Sharlow
Elizabeth R
ER
Napper
Andrew D
AD
Huryn
Donna M
DM
Cooperman
Barry S
BS
Smith
Amos B
AB
Diamond
Scott L
SL
D000818:Animals; D001011:Aorta / Q000166:cytology; D001665:Binding Sites; D056668:Cathepsin L; D002403:Cathepsins / Q000032:analysis / Q000037:antagonists & inhibitors*; D002478:Cells, Cultured; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000032:analysis; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry* / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D020128:Inhibitory Concentration 50; D007700:Kinetics; D018320:Leishmania major / Q000187:drug effects; D008956:Models, Chemical; D015394:Molecular Structure; D010206:Papain / Q000737:chemistry; D010963:Plasmodium falciparum / Q000187:drug effects; D011485:Protein Binding; D012680:Sensitivity and Specificity
D015853:Cysteine Proteinase Inhibitors; D002403:Cathepsins; D003546:Cysteine Endopeptidases; C534281:CTSL protein, human; D056668:Cathepsin L; D010206:Papain