Comparative inhibitory effect of safranin O on cholinesterases

Önder S., Sarı S., Tacal Ö.

31. Ulusal Biyokimya Kongresi, 18 - 20 December 2020, pp.39-40

  • Publication Type: Conference Paper / Summary Text
  • Page Numbers: pp.39-40
  • Hacettepe University Affiliated: Yes


OBJECTIVES: Inhibition of cholinesterases is a mainstay strategy in the treatment of Alzheimer’s disease (AD) that involves critical loss of acetylcholine in the central nervous system. Recently, we have shown that a phenazine-derived synthetic dye, methylene violet 3RAX is an effective inhibitor of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). In the present study, the inhibitory mechanism and effect of a synthetic phenazine dye, safranin O (SO) on human erythrocyte AChE, human plasma BChE and recombinant BChE mutants (A328F and A328Y) was studied for comparison.

MATERIALS and METHODS: AChE and BChE activities were assayed spectrophotometrically in 50 mM MOPS buffer (pH 8) containing 0.05-0.4 mM acetylthiocholine or butyrylthiocholine as substrate, 0.125 mM DTNB and 0-40 μM SO at 25°C. Initial rate data were analyzed using a simplified rapid equilibrium model for mixed inhibition The kinetic results were supported by molecular modelling studies.

RESULTS: SO leaded to linear competitive inhibition of human plasma BChE (Ki=0.44± 0.085 μM; α=∞) and hyperbolic noncompetitive inhibition of human erythrocyte AChE (Ki=0.69±0.13; α=1; β=0.08). On the other hand, SO caused linear mixed type inhibition of A328F (Ki=0.033± 0.003 μM; α=45±9) and A328Y BChE mutants (Ki=0.078±0.014 μM; α=74±30). The molecular modelling results showed that human BChE’s affinity against SO increases with replacement of Ala328 to Phe or Tyr.

CONCLUSIONS: SO is a potent inhibitor of cholinesterases and may be useful in the design and development of new drugs for the treatment of AD.

Keywords: Safranin O, Cholinesterase İnhibition, Acetylcholinesterase, Butyrylcholinesterase, Molecular Docking