Biochemical characterization of catalase, an important antioxidant enzyme in Leptospira interrogans

IGLESIAS, AA; SASONI, N; ARIAS, DG; GUERRERO, SA

Salta

Congreso; SAIB LV Reunión Anual; 2019

SAIB

Catalase is an abundant protein and a virulencefactor in Leptospira interrogans.Although the pathogenic and non‑pathogenic strains of Leptospiras have genescoding for catalase in their genomes, these are not homologous proteins andbelong to different enzyme groups. Catalase is responsible for tolerance toexogenous oxidative species by L. interrogans.It was reported that pathogenic species (such as L. interrogans) have strong catalase activity and low peroxidaseactivity, while non-pathogenic species (such as L. biflexa) show only peroxidase activity, which suggests thatcatalase plays an important role during infection in the mammalian host. Inthis work, we studied biochemical properties of catalase of L. interrogans. The enzyme obtained byrecombinant expression in Escherichiacoli presented a homo-tetrameric structure. An amino acid sequence analysisindicated that the enzyme belong to mono-functional catalases, however, its functionalcharacteristics suggest that the protein could be a bi-functional enzyme. Both tert-butyl hydroperoxide (t-BuOOH, an organic hydroperoxide) andHClO exhibited an inhibitory effect on catalase activity. On the other hand, HClOinhibition brought changes in its oligomeric structure, with the consequentformation of high molecular mass oligomers. Alternatively, nitrosocysteine (CySNO)caused substrate-reversible nitrosylation on the protein heme group, withoutchange in its oligomeric structure. By western blot assays, we detected thatcatalase relative abundance was modified when L. interrogans is exposed to exogenous CySNO or HClO but not with H2O2or t‑BuOOH. The results obtainedindicate that the structure-function relationship of the protein is regulatedin the presence of different types of redox agents. Granted by ANPCyT (PICT2014-2103, PICT2016-1778 andPICT2017-2268).