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

British journal of pharmacology (2013-03-16)
Antonia Asimakopoulou, Panagiotis Panopoulos, Christos T Chasapis, Ciro Coletta, Zongmin Zhou, Giuseppe Cirino, Athanassios Giannis, Csaba Szabo, Georgios A Spyroulias, Andreas Papapetropoulos

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

Product Number
Product Description

D-Cysteine, ≥99% (RT)

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