The catalytic activity of GR (EC 1.8.1.7) was determined following
the methodology proposed by Goldberg and Spooner (1987), as described
by Vázquez-Medina et al. (2006). The results are expressed
in units of GR mg−1 of protein. One unit of GR is defined as the
amount of enzyme required to reduce 1 mol of GSSG to GSH per min.