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Published on: August 31, 2015
Inhibitors of GapN-dependent NADPH supply as potential lead compounds for novel therapeutics against Streptococcus
Isabell Schütt1, Philip Einwohlt1, Anna-Maria Wandinger2
1Institute of Medical Microbiology, Virology, and Hygiene, Rostock University Medical Center, Rostock, Germany.
Abstract:
Infections with Streptococcus pyogenes are among the most important diseases caused by bacteria and are responsible for around 500,000 deaths every year. In 2024, macrolide-resistant S. pyogenes was added to the WHO's list of priority pathogens. The non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase GapN has been identified as a potential drug target in S. pyogenes. SpyGapN is the major NADP-reducing enzyme in these bacteria as they lack the oxidative part of the pentose phosphate pathway. In this study, in silico docking of compound libraries to the glyceraldehyde 3-phosphate binding pocket of SpyGapN was used to screen for potential competitive inhibitors. Among the candidates identified with this approach, 1,2-dihydroxyethane-1,2-disulfonate (glyoxal bisulfite) showed the strongest inhibition of SpyGapN activity in vitro. In a complementary approach, crystallographic fragment screening was conducted, which identified the ultra-low-molecular-weight compounds pyrimidine-5-amine and 4-hydroxypyridazine targeting the cofactor-binding pocket of SpyGapN. Both low-molecular-weight compounds were experimentally confirmed to inhibit the activity of purified SpyGapN. Combinations of glyoxal bisulfite with either pyrimidine-5-amine or 4-hydroxypyridazine enhanced the inhibitory effect of SpyGapN. Glyoxal bisulfite was able to kill S. pyogenes. This effect was accelerated by combining glyoxal bisulfite with 4-hydroxypyridazine. While these findings suggest that inhibition of SpyGapN probably contributes to the observed antibacterial activity, the exact mechanism of action remains to be confirmed, as the compounds also affect other G3P-converting enzymes. Nevertheless, these compounds provide a promising starting point for the development of more specific SpyGapN inhibitors.
Insights
New drug candidates targeting the GapN enzyme in Streptococcus pyogenes show promise for combating this priority pathogen. Glyoxal bisulfite and other compounds effectively inhibit GapN and kill bacteria, offering a potential new strategy against resistant infections.
Area of Science:
- Biochemistry
- Microbiology
- Drug Discovery
Background:
- Streptococcus pyogenes causes significant global mortality, with increasing macrolide resistance making it a WHO priority pathogen.
- The bacterial enzyme non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GapN) is a potential drug target in S. pyogenes.
- SpyGapN is crucial for NADP reduction in S. pyogenes due to the absence of the oxidative pentose phosphate pathway.
Purpose of the Study:
- To identify and characterize novel competitive inhibitors of SpyGapN.
- To evaluate the antibacterial activity of identified inhibitors against S. pyogenes.
- To explore combination therapies for enhanced inhibition and bacterial killing.
Main Methods:
- In silico molecular docking of compound libraries to the SpyGapN glyceraldehyde 3-phosphate binding pocket.
- In vitro enzymatic assays to measure SpyGapN inhibition.
- Crystallographic fragment screening to identify compounds binding to the cofactor pocket.
- In vitro antibacterial assays to assess bacterial killing.
Main Results:
- 1,2-dihydroxyethane-1,2-disulfonate (glyoxal bisulfite) emerged as a potent inhibitor of SpyGapN.
- Pyrimidine-5-amine and 4-hydroxypyridazine were identified as low-molecular-weight inhibitors targeting the cofactor pocket.
- Combinations of glyoxal bisulfite with pyrimidine-5-amine or 4-hydroxypyridazine showed enhanced SpyGapN inhibition.
- Glyoxal bisulfite demonstrated bactericidal activity against S. pyogenes, enhanced by 4-hydroxypyridazine.
Conclusions:
- Glyoxal bisulfite, pyrimidine-5-amine, and 4-hydroxypyridazine are promising starting points for developing specific SpyGapN inhibitors.
- Inhibition of SpyGapN likely contributes to the antibacterial effects observed, though further mechanistic studies are needed.
- These compounds offer a potential new avenue for treating infections caused by the priority pathogen Streptococcus pyogenes.
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