Comparative effects of cationic triarylmethane, phenoxazine and phenothiazine dyes on horse serum butyrylcholinesterase |
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Authors: | Yücel Yasemin Yücel Tacal Ozden Ozer Inci |
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Institution: | Department of Biochemistry, School of Pharmacy, Hacettepe University, 06100 Ankara, Turkey |
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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 °C in 50 mM MOPS buffer, pH 8, using butyrylthiocholine as substrate. PR, MeG, MB and ethopropazine acted as linear mixed type inhibitors of the enzyme, with respective Ki values of 4.5 ± 0.50 μM, 0.41 ± 0.007 μM, 0.44 ± 0.086 μM and 0.050 ± 0.0074 μM. MG, NB, MethB and NR caused complex, nonlinear inhibition pointing to cooperative binding at two sites. Intrinsic K′ values (≡I]20.5 extrapolated to S]=0) for MG, NB, NR and MethB were 0.20 ± 0.096 μM, 0.0018 ± 0.0015 μM, 0.92 ± 0.23 μM and 0.23 ± 0.08 μM. 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. |
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Keywords: | Horse serum butyrylcholinesterase Triarylmethane dyes Phenoxazine dyes Phenothiazine dyes Cholinesterase inhibition Nile blue |
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