title: Development of a homogeneous time-resolved fluorescence assay for high throughput screening to identify Lck inhibitors: comparison with scintillation proximity assay and streptavidin-coated plate assay.
abstract: This study details the development of a homogeneous time-resolved fluorescence (HTRF) high throughput screening assay to identify inhibitors of Lck. HTRF was compared with scintillation proximity and streptavidin-coated plate assays. Because of the differences in the sensitivity of detection of phosphotyrosine among the three assays, different amounts of enzyme were used. However, the concentrations of the other assay components were standardized. When using similar assay conditions, the calculated IC(50) values of inhibitory compounds were independent of assay format. Furthermore, filtration experiments revealed that phosphorylation of a biotinyl poly-Glu,Ala, Tyr peptide substrate was less than autophosphorylation of the Lck enzyme; this was due to the low K(m) value for biotinyl poly-Glu,Ala,Tyr. In the HTRF assay, small amounts of enzyme and high concentrations of ATP could be used, thereby minimizing the effects of autophosphorylation. Higher ATP concentration would also minimize the effect of ATP competitors. Using this technology, it may be possible to find novel kinase inhibitors that do not act at the ATP binding site of protein tyrosine kinases.
authors.affiliation: Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co., Ltd., Ibaraki 305-8585, Japan. oomi@yamanouchi.co.jp
authors.forename: N
authors.initials: N
authors.lastname: Ohmi
authors.forename: J M
authors.initials: JM
authors.lastname: Wingfield
authors.forename: H
authors.initials: H
authors.lastname: Yazawa
authors.forename: O
authors.initials: O
authors.lastname: Inagaki
mesh_terms: D001710:Biotin; D004353:Drug Evaluation, Preclinical / Q000379:methods*; D004791:Enzyme Inhibitors / Q000032:analysis* / Q000494:pharmacology; D005453:Fluorescence; D066298:In Vitro Techniques; D007700:Kinetics; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012588:Scintillation Counting; D019809:Streptavidin; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; D010455:Peptides; D011994:Recombinant Proteins; D001710:Biotin; D019809:Streptavidin; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)