Selectivity of commonly used pharmacological inhibitors for cystathionine β synthase (CBS) and cystathionine γ lyase (CSE)

Br J Pharmacol. 2013 Jun;169(4):922-32. doi: 10.1111/bph.12171.


Background and purpose: Hydrogen sulfide (H₂S) is a signalling molecule that belongs to the gasotransmitter family. Two major sources for endogenous enzymatic production of H₂S are cystathionine β synthase (CBS) and cystathionine γ lyase (CSE). In the present study, we examined the selectivity of commonly used pharmacological inhibitors of H₂S biosynthesis towards CSE and CBS.

Experimental approach: To address this question, human CSE or CBS enzymes were expressed and purified from Escherichia coli as fusion proteins with GSH-S-transferase. After purification, the activity of the recombinant enzymes was tested using the methylene blue method.

Key results: β-Cyanoalanine (BCA) was more potent in inhibiting CSE than propargylglycine (PAG) (IC₅₀ 14 ± 0.2 μM vs. 40 ± 8 μM respectively). Similar to PAG, L-aminoethoxyvinylglycine (AVG) only inhibited CSE, but did so at much lower concentrations. On the other hand, aminooxyacetic acid (AOAA), a frequently used CBS inhibitor, was more potent in inhibiting CSE compared with BCA and PAG (IC₅₀ 1.1 ± 0.1 μM); the IC₅₀ for AOAA for inhibiting CBS was 8.5 ± 0.7 μM. In line with our biochemical observations, relaxation to L-cysteine was blocked by AOAA in aortic rings that lacked CBS expression. Trifluoroalanine and hydroxylamine, two compounds that have also been used to block H₂S biosynthesis, blocked the activity of CBS and CSE. Trifluoroalanine had a fourfold lower IC₅₀ for CBS versus CSE, while hydroxylamine was 60-fold more selective against CSE.

Conclusions and implications: In conclusion, although PAG, AVG and BCA exhibit selectivity in inhibiting CSE versus CBS, no selective pharmacological CBS inhibitor is currently available.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / analogs & derivatives
  • Alanine / pharmacology
  • Alkynes / pharmacology
  • Animals
  • Aorta, Thoracic / drug effects
  • Aorta, Thoracic / enzymology
  • Aorta, Thoracic / metabolism
  • Cystathionine beta-Synthase / antagonists & inhibitors*
  • Cystathionine beta-Synthase / genetics
  • Cystathionine beta-Synthase / metabolism
  • Cystathionine gamma-Lyase / antagonists & inhibitors*
  • Cystathionine gamma-Lyase / genetics
  • Cystathionine gamma-Lyase / metabolism
  • Enzyme Inhibitors / pharmacology*
  • Glutathione Transferase / chemistry
  • Glutathione Transferase / genetics
  • Glutathione Transferase / metabolism
  • Glycine / analogs & derivatives
  • Glycine / pharmacology
  • Humans
  • Hydrogen Sulfide / analysis
  • Hydrogen Sulfide / metabolism
  • In Vitro Techniques
  • Kinetics
  • Nitric Oxide / metabolism
  • Nitric Oxide Donors / pharmacology
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Vasodilation / drug effects


  • Alkynes
  • Enzyme Inhibitors
  • Nitric Oxide Donors
  • Peptide Fragments
  • Recombinant Fusion Proteins
  • Nitric Oxide
  • propargylglycine
  • 3-cyanoalanine
  • Glutathione Transferase
  • Cystathionine beta-Synthase
  • Cystathionine gamma-Lyase
  • Alanine
  • aminoethoxyvinylglycine
  • Glycine
  • Hydrogen Sulfide