Detection, purification and partial characterization of beta-amylase from trophozoites of Entamoeba invadens

Revisiting Drug Development Against the Neglected Tropical Disease, Amebiasis

Amebiasis is a neglected tropical disease which is caused by the protozoan parasite Entamoeba histolytica. This disease is one of the leading causes of diarrhea globally, affecting largely impoverished residents in developing countries. Amebiasis also remains one of the top causes of gastrointestinal diseases in returning international travellers. Despite having many side effects, metronidazole remains the drug of choice as an amebicidal tissue-active agent. However, emergence of metronidazole resistance in pathogens having similar anaerobic metabolism and also in laboratory strains of E. histolytica has necessitated the identification and development of new drug targets and therapeutic strategies against the parasite. Recent research in the field of amebiasis has led to a better understanding of the parasite’s metabolic and cellular pathways and hence has been useful in identifying new drug targets. On the other hand, new molecules effective against amebiasis have been mined by modifying available compounds, thereby increasing their potency and efficacy and also by repurposing existing approved drugs. This review aims at compiling and examining up to date information on promising drug targets and drug molecules for the treatment of amebiasis.

Halophilic alkali- and thermostable amylase from a novel polyextremophilic Amphibacillus sp. NM-Ra2

Extracellular gluco-amylo-pullulanase from Amphibacillus sp. NM-Ra2 was purified to homogeneity by ethanol precipitation, anion exchange chromatography and gel filtration chromatography. Molecular mass of the enzyme was 50kDa (SDS-PAGE). The enzyme showed maximal activity at 1.9 M NaCl, pH50°C 8.0 and 54°C and was active from 0 to 4.3 M NaCl and 37 to 65°C. The enzyme was inhibited by EDTA and was stable and active in the presence of PMSF, DTT, H2O2, Triton-X-100, Tween 20 and Tween 80. Ca2+ is inessential for activity. The amylase was stimulated with K+ and inhibited with Cu2+ and Mg2+. Hg2+, Zn2+ and Fe2+ had no effect on activity. Amylase was stable and active in the presence of ethanol, methanol and benzene (25%, v/v). The enzyme hydrolyzed linear and branched polysaccharides including pullulan, glycogen and amylopectin, and hydrolyzed raw wheat starch and raw corn starch (14.6% and 13.5% over 2 h). Amylase activity was inhibited by soluble starch concentrations greater than 0.3%. The major products of soluble starch hydrolysis were maltose and maltotriose. The amylase, being halophilic and alkali-thermostable, in addition to being resistant to surfactants, oxidizing agents and organic solvents, can find applications in the starch processing, pharmaceutical, food and paper/pulp industries.