title: Molecular insights into substrate specificity of prostate specific antigen through structural modeling.
abstract: Prostate Specific Antigen's (PSA) role as a biomarker for prostate cancer is well established but the physiological role of its serine protease activity in the pathobiology of normal prostate and prostate carcinogenesis remains largely unknown. In light of recent studies that implicate PSA's enzymatic activity in the initiation and/or progression of prostate cancer, we performed a molecular modeling study of substrate binding at the catalytic site of PSA wherein a PSA-selective substrate (HSSKLQ) was docked in an acyl-enzyme conformation to a three-dimensional homology model of PSA. Additionally, virtual positional scanning studies were conducted to gain mechanistic insights into substrate recognition of PSA. Subsequently, 13 novel peptide substrates of 6-aa length and four peptide substrates with varying length were synthesized and assayed for PSA hydrolysis to evaluate the experimental validity of docking insights. Additionally, six novel aldehyde-containing transition state analog inhibitors were synthesized and tested for their inhibitory potencies. The experimental data on the hydrolysis rates of the newly synthesized substrates and inhibitory potencies of the aldehyde peptides agreed with the docking predictions, providing validation of the docking methodology and demonstrating its utility towards the design of substrate-mimetic inhibitors that can be used to explore PSA's role in the pathobiology of prostate cancer.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Johns Hopkins University Whiting School of Engineering, Baltimore, Maryland 21218, USA. psingh@jhu.edu
authors.forename: Pratap
authors.initials: P
authors.lastname: Singh
authors.forename: Aaron M
authors.initials: AM
authors.lastname: LeBeau
authors.forename: Hans
authors.initials: H
authors.lastname: Lilja
authors.forename: Samuel R
authors.initials: SR
authors.lastname: Denmeade
authors.forename: John T
authors.initials: JT
authors.lastname: Isaacs
mesh_terms: D000465:Algorithms; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D003198:Computer Simulation; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008297:Male; D008958:Models, Molecular; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D017430:Prostate-Specific Antigen / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D013379:Substrate Specificity
chemical_list: D008024:Ligands; D009842:Oligopeptides; D010446:Peptide Fragments; D015842:Serine Proteinase Inhibitors; D017430:Prostate-Specific Antigen
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