Inhibiting Pyridoxal Kinase of Entamoeba histolytica Is Lethal for This Pathogen

Area of Science:

• Biochemistry
• Parasitology
• Drug Discovery

Background:

• Pyridoxal 5'-phosphate (PLP) is a vital cofactor for numerous enzymes essential for microbial survival.
• Entamoeba histolytica, a protozoan parasite causing amoebiasis, cannot synthesize vitamin B6 and relies on host uptake.
• PLP-dependent enzymes, particularly pyridoxal kinase (EhPLK), are potential drug targets due to their essential role and distinct active sites compared to human homologs.

Purpose of the Study:

• To identify and evaluate small molecules that inhibit EhPLK as potential therapeutic agents against Entamoeba histolytica.

Main Methods:

• In-silico screening of small molecule libraries against EhPLK.
• Molecular docking to predict binding affinity and mode.
• In-vitro testing of selected compounds for enzyme inhibition (IC50 determination).
• Assessment of compound efficacy on Entamoeba trophozoite growth in cultured cells.

Main Results:

• Five compounds were shortlisted based on docking scores, showing potential to bind the PLP site and inhibit substrate binding.
• Two compounds demonstrated significant in-vitro inhibitory activity with IC50 values between 100-250 μM.
• These two compounds drastically reduced Entamoeba trophozoite growth by over 90% within 72 hours in cell culture.

Conclusions:

• EhPLK is a validated drug target for Entamoeba histolytica.
• The identified small molecules show potent anti-parasitic activity by inhibiting EhPLK.
• These findings support the development of novel therapeutics for amoebiasis targeting the vitamin B6 pathway.