Inhibiting Pyridoxal Kinase of Entamoeba histolytica Is Lethal for This Pathogen. 2021

Suneeta Devi, and Priya Tomar, and Khaja Faisal Tarique, and Samudrala Gourinath
Structural Biology Laboratory, School of Life Sciences, Jawaharlal Nehru University, New Delhi, India.

Pyridoxal 5'-phosphate (PLP) functions as a cofactor for hundreds of different enzymes that are crucial to the survival of microorganisms. PLP-dependent enzymes have been extensively characterized and proposed as drug targets in Entamoeba histolytica. This pathogen is unable to synthesize vitamin B6 pathway and relies on the uptake of vitamin B6 vitamers from the host which are then phosphorylated by the enzyme pyridoxal kinase to produce PLP, the active form of vitamin B6. Previous studies from our lab shows that EhPLK is essential for the survival and growth of this protozoan parasite and its active site differs significantly with respect to its human homologue making it a potential drug target. In-silico screening of EhPLK against small molecule libraries were performed and top five ranked molecules were shortlisted on the basis of docking scores. These compounds dock into the PLP binding site of the enzyme such that binding of these compounds hinders the binding of substrate. Of these five compounds, two compounds showed inhibitory activity with IC50 values between 100-250 μM when tested in-vitro. The effect of these compounds proved to be extremely lethal for Entamoeba trophozoites in cultured cells as the growth was hampered by 91.5% and 89.5% when grown in the presence of these compounds over the period of 72 hours.

UI MeSH Term Description Entries
D011731 Pyridoxal Kinase An enzyme that catalyzes reversibly the phosphorylation of pyridoxal in the presence of ATP with the formation of pyridoxal 5-phosphate and ADP. Pyridoxine, pyridoxamine and various derivatives can also act as acceptors. EC 2.7.1.35. Pyridoxamine Kinase,Pyridoxine Kinase,Pyridoxal Phosphokinase,Kinase, Pyridoxal,Kinase, Pyridoxamine,Kinase, Pyridoxine,Phosphokinase, Pyridoxal
D011732 Pyridoxal Phosphate This is the active form of VITAMIN B 6 serving as a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, aminolevulinic acid. During transamination of amino acids, pyridoxal phosphate is transiently converted into pyridoxamine phosphate (PYRIDOXAMINE). Pyridoxal 5-Phosphate,Pyridoxal-P,Phosphate, Pyridoxal,Pyridoxal 5 Phosphate,Pyridoxal P
D004748 Entamoeba histolytica A species of parasitic protozoa causing ENTAMOEBIASIS and amebic dysentery (DYSENTERY, AMEBIC). Characteristics include a single nucleus containing a small central karyosome and peripheral chromatin that is finely and regularly beaded. Endamoeba histolytica,histolytica, Endamoeba
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D053058 Trophozoites Cells or feeding stage in the life cycle of sporozoan protozoa. In the malarial parasite, the trophozoite develops from the MEROZOITE and then splits into the SCHIZONT. Trophozoites that are left over from cell division can go on to form gametocytes. Trophozoite
D025101 Vitamin B 6 VITAMIN B 6 refers to several PICOLINES (especially PYRIDOXINE; PYRIDOXAL; & PYRIDOXAMINE) that are efficiently converted by the body to PYRIDOXAL PHOSPHATE which is a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, and aminolevulinic acid. During transamination of amino acids, pyridoxal phosphate is transiently converted into PYRIDOXAMINE phosphate. Although pyridoxine and Vitamin B 6 are still frequently used as synonyms, especially by medical researchers, this practice is erroneous and sometimes misleading (EE Snell; Ann NY Acad Sci, vol 585 pg 1, 1990). Most of vitamin B6 is eventually degraded to PYRIDOXIC ACID and excreted in the urine. Vitamin B6

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