The metabolic connection between Methionine and Cysteine: a relevant aspect of the sulfur metabolism in Trypanosoma cruzi

• Grant number: 23/07669-5
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• Start date: December 01, 2023
• End date: November 30, 2027
• Field of knowledge: Biological Sciences - Biochemistry - Metabolism and Bioenergetics
• Principal Investigator: Ariel Mariano Silber
• Grantee: Karina Paola Buitrón Buitrón
• Host Institution: Instituto de Ciências Biomédicas (ICB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 21/12938-0 - Amino acid metabolism in Trypanosoma cruzi: a toolbox to survive in hostile environments, AP.TEM

Abstract

There are indications of the existence of a transsulfuration pathway in T. cruzi that would enable the synthesis of Cys from Met. The existence of this pathway could have great relevance in the metabolism of sulfur and in the production of sulfur metabolites, whose reduced state works as a reserve of reducing power and, therefore, is one of the bases of cell defenses against oxidative imbalance. Initially, the activation of Met, which is the donor of the sulfur atom, occurs through its reaction with ATP, forming S-adenosyl-L-methionine in a reaction catalyzed by S-adenosylmethionine synthetase. The second reaction, the conversion of S-adenosyl-L-methionine to S-adenosyl-L-homocysteine would be catalyzed by an S-adenosyl-L-methionine methyltransferase or a (Cytosine-5)-methyltransferase. None of these enzyme activities, nor putative genes for these enzymes have been found so far. However, literature data allow inferring the existence of this catalytic step in the parasite. As for the third enzyme of the homocysteine synthesis pathway, catalyzed by S-Adenosilhomocysteine hydrolase. Interestingly, starting from homocysteine, Met can be produced again, through a Homocysteine S-Methyltransferase, thus closing a cycle whose biological function is still not well understood. Therefore, we propose: 1. Cloning, expressing, biochemically characterizing and obtaining antibodies against the enzymes S-adenosylmethionine Synthetase, S-Adenosilhomocysteine Hydrolase, Homocysteine S-Methyltransferase; 2. Evaluate the phenotype of cells treated with specific inhibitors of the enzymes S-adenosylmethionine Synthetase, S-Adenosilhomocysteine Hydrolase, Homocysteine S-Methyltransferase; 3. Obtaining T. cruzi strains with the coding genes for the enzymes S-adenosylmethionine Synthetase and/or S-Adenosilhomocysteine Hydrolase (enzymes of the transsulfation cycle), deleted by CRISPR/Cas9. Phenotypic evaluation of these strains. (AU)