Conferring specificity in redox pathways by enzymatic thiol/disulfide exchange reactions

Author(s)

Netto, Luis Eduardo S. ^[1] ; de Oliveira, Marcos Antonio ^[2] ; Tairum, Carlos A. ^[2] ; da Silva Neto, Jose Freire ^[3]

Affiliation

^[1] Univ Sao Paulo, Inst Biociencias, Dept Genet & Biol Evolut, BR-05508090 Sao Paulo - Brazil

^[2] Univ Estadual Paulista, Dept Biol, Campus Litoral Paulista Sao Vicente, Sao Paulo - Brazil

^[3] Univ Sao Paulo, Fac Med Ribeirao Preto, Dept Biol Celular & Mol & Bioagentes Patogen, BR-14049 Ribeirao Preto, SP - Brazil

• Document type: Review article
• Source: Free Radical Research; v. 50, n. 2, p. 206-245, FEB 1 2016.
• Web of Science Citations: 22

Abstract

Thiol-disulfide exchange reactions are highly reversible, displaying nucleophilic substitutions mechanism (S(N)2 type). For aliphatic, low molecular thiols, these reactions are slow, but can attain million times faster rates in enzymatic processes. Thioredoxin (Trx) proteins were the first enzymes described to accelerate thiol-disulfide exchange reactions and their high reactivity is related to the high nucleophilicity of the attacking thiol. Substrate specificity in Trx is achieved by several factors, including polar, hydrophobic, and topological interactions through a groove in the active site. Glutaredoxin (Grx) enzymes also contain the Trx fold, but they do not share amino acid sequence similarity with Trx. A conserved glutathione binding site is a typical feature of Grx that can reduce substrates by two mechanisms (mono and dithiol). The high reactivity of Grx enzymes is related to the very acid pK(a) values of reactive Cys that plays roles as good leaving groups. Therefore, although distinct oxidoreductases catalyze similar thiol-disulfide exchange reactions, their enzymatic mechanisms vary. PDI and DsbA are two other oxidoreductases, but they are involved in disulfide bond formation, instead of disulfide reduction, which is related to the oxidative environment where they are found. PDI enzymes and DsbC are endowed with disulfide isomerase activity, which is related with their tetra-domain architecture. As illustrative description of specificity in thiol-disulfide exchange, redox aspects of transcription activation in bacteria, yeast, and mammals are presented in an evolutionary perspective. Therefore, thiol-disulfide exchange reactions play important roles in conferring specificity to pathways, a required feature for signaling. (AU)

• FAPESP's process: 13/07937-8 - Redoxome - Redox Processes in Biomedicine
• Grantee: Ohara Augusto
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC