Disulfiram as a novel inactivator of Giardia lamblia triosephosphate isomerase with antigiardial potential.

Giardiasis, the infestation of the intestinal tract by Giardia lamblia, is one of the most prevalent parasitosis worldwide. Even though effective therapies exist for it, the problems associated with its use indicate that new therapeutic options are needed. It has been shown that disulfiram eradicates trophozoites in vitro and is effective in vivo in a murine model of giardiasis; disulfiram inactivation of carbamate kinase by chemical modification of an active site cysteine has been proposed as the drug mechanism of action. The triosephosphate isomerase from G. lamblia (GlTIM) has been proposed as a plausible target for the development of novel antigiardial pharmacotherapies, and chemical modification of its cysteine 222 (C222) by thiol-reactive compounds is evidenced to inactivate the enzyme. Since disulfiram is a cysteine modifying agent and GlTIM can be inactivated by modification of C222, in this work we tested the effect of disulfiram over the recombinant and trophozoite-endogenous GlTIM. The results show that disulfiram inactivates GlTIM by modification of its C222. The inactivation is species-specific since disulfiram does not affect the human homologue enzyme. Disulfiram inactivation induces only minor conformational changes in the enzyme, but substantially decreases its stability. Recombinant and endogenous GlTIM inactivates similarly, indicating that the recombinant protein resembles the natural enzyme. Disulfiram induces loss of trophozoites viability and inactivation of intracellular GlTIM at similar rates, suggesting that both processes may be related. It is plausible that the giardicidal effect of disulfiram involves the inactivation of more than a single enzyme, thus increasing its potential for repurposing it as an antigiardial drug.

[Mutation analysis of the methylmalonyl-CoA mutase gene in ten Mexican patients with methylmalonic acidemia]. / Análisis de mutaciones en el gen de la metilmalonilCoA mutasa en diez pacientes mexicanos con acidemia metilmalónica aislada.

INTRODUCTION: Methylmalonic acidemia (MMA) is a genetically determined human metabolic disease, characterized by deficient activity of the mitochondrial enzyme, methylmalonyl CoA mutase (MCM). This enzyme catalyzes the isomerization of L-methylmalonyl CoA to succinyl CoA and requires adenosylcobalamin as cofactor. Several mutations have been identified in the unique genetic locus encoding the MCM apoenzyme (mut) which causes MMA. AIM: To identify the mutations present in Mexican patients diagnosed with MMA. RESULTS: Complete nucleotide sequencing of mut gene exons of 10 Mexican patients with methylmalonic acidemia (MMA) identified one novel mutation and eight mutations previously reported in the methylmalonyl-CoA mutase (mut) gene. The new mutation c.406G > T (p.V136F) was found in one patient combined with the deletion c.1891delG (p.A631QfsX17). The missense mutation c.322C > T (p.R108C) was found in six non-related patients; in addition, the mutations c.ins671-678dupAATTTATG (p.V227NfsX16), c.682C > T (p.R228X), c1022-1023dupA (p. N341KfsX20), c.1846C > T (p.R616C), c.2080C > T (p.R694W), and c.385+3insTAAGGGT (splice) were found. This work reveals that Mexican patients with MMA have new (p.V136F) as well as worldwide and hispanic reported mutations. The mutation R108C is the most frequent change (40% of total alleles) mainly in patients from León, Guanajuato.