S-NITROSYLATION OF HUMAN TRIOSEPHOSHATE ISOMERASE: STRUCTURAL AND BIOCHEMICAL STUDIES

ROMERO, JORGE M.; CARRIZO, MARÍA E.; CURTINO, JUAN A.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Nitric oxide (NO) is a diatomic gaseous free radical produced in large amounts by macrophages upon the induction of NO synthetase. One of the mayor consequences of NO exposure is the generation of the protein S-nitrosylation, which could produce alterations in protein function. Even though the S-nitrosylation mechanism in vivo is unclear, several reactive nitrogen species were proposed as mediators including NO gas, or non protein S-nitrosothiols such as S-nitrosocysteine (CySNO) and S-nitrosoglutathione (GSNO). Triosephosphate isomerase (TPI) has been frequently identified as a target of S-nitrosylation by proteomic studies. TPI is a dimeric enzyme that catalyzes the isomerization of dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (G3P), and it is found in almost all organisms. However, the effect of S-nitrosylation on activity were only explored in plants and algae. Here, we present results about the S-nitrosylation of human TPI (hTPI), and the effect on its enzymatic parameters. hTPI is S-nitrosylated by S-transnitrosylation mechanism in a time-dependent manner by both, CySNO and GSNO, being CySNO more efficient. Both, X-ray crystal structure and mass spectrometry analysis showed that Cys217 was S-nitrosylated just in one subunit of the dimer. hTPI S-nitrosylation produced a 15% inhibition of the Vmax of the DHAP to G3P conversion. However, we did not observe effect on the Km. This is the first in vitro study of the hTPI S-nitrosylation. Further studies will be required to identify the structural basis of the inhibition.