title: Comparative effects of cationic triarylmethane, phenoxazine and phenothiazine dyes on horse serum butyrylcholinesterase.
abstract: The kinetic effects of a selection of triarylmethane, phenoxazine and phenothiazine dyes (pararosaniline (PR), malachite green (MG), methyl green (MeG); meldola blue (MB), nile blue (NB), nile red (NR); methylene blue (MethB)) and of ethopropazine on horse serum butyrylcholinesterase were studied spectrophotometrically at 25( degrees )C in 50mM MOPS buffer, pH 8, using butyrylthiocholine as substrate. PR, MeG, MB and ethopropazine acted as linear mixed type inhibitors of the enzyme, with respective K(i) values of 4.5+/-0.50 microM, 0.41+/-0.007 microM, 0.44+/-0.086 microM and 0.050+/-0.0074 microM. MG, NB, MethB and NR caused complex, nonlinear inhibition pointing to cooperative binding at two sites. Intrinsic K' values ( identical with[I](2)(0.5) extrapolated to [S]=0) for MG, NB, NR and MethB were 0.20+/-0.096 microM, 0.0018+/-0.0015 microM, 0.92+/-0.23 microM and 0.23+/-0.08 microM. NB stood out as a potent inhibitor effective at nM levels. Comparison of inhibitory effects on horse and human serum butyrylcholinesterases suggested that the two enzymes must have distinct microstructural features.
authors.affiliation: Department of Biochemistry, School of Pharmacy, Hacettepe University, 06100 Ankara, Turkey.
authors.forename: Yasemin Yücel
authors.initials: YY
authors.lastname: Yücel
authors.forename: Ozden
authors.initials: O
authors.lastname: Tacal
authors.forename: Inci
authors.initials: I
authors.lastname: Ozer
mesh_terms: D000818:Animals; D002091:Butyrylcholinesterase / Q000097:blood* / Q000737:chemistry; D002800:Cholinesterase Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D004396:Coloring Agents / Q000494:pharmacology; D006736:Horses / Q000097:blood; D066298:In Vitro Techniques; D007700:Kinetics; D008697:Methane / Q000031:analogs & derivatives / Q000494:pharmacology; D008739:Methyl Green / Q000494:pharmacology; D008954:Models, Biological; D010078:Oxazines / Q000494:pharmacology; D010640:Phenothiazines / Q000494:pharmacology; D012394:Rosaniline Dyes / Q000494:pharmacology; D014052:Toluidines / Q000494:pharmacology
chemical_list: D002800:Cholinesterase Inhibitors; D004396:Coloring Agents; D010078:Oxazines; D010640:Phenothiazines; D012394:Rosaniline Dyes; D014052:Toluidines; C005409:pararosaniline; C005559:Meldola blue; C084820:profenamine; D008739:Methyl Green; C039203:phenoxazine; D002091:Butyrylcholinesterase; D008697:Methane