Strict criteria prove that the catalase activity is intrinsic properties of scz-IgG<sub>mix</sub> and health-IgG<sub>mix</sub>.

<p>Preparations of scz-IgG<sub>mix</sub> (<b>A</b>) and healthy-IgG<sub>mix</sub> (<b>B</b>) were separated by FPLC gel filtration on a Superdex 200 column in an acidic buffer Gly-HCl pH 2.6 after Abs incubation in the same buffer: (—), absorbance at 280 nm (A<sub>280</sub>); (○), relative activity (RA) of the IgG<sub>mix</sub> in the degradation of H<sub>2</sub>O<sub>2</sub>. Analysis of the thermal stability of scz-IgG<sub>mix</sub>; the preparation was preincubated at various temperatures for 10 minutes and then its relative catalytic activity was estimated using standard conditions (C). SDS-PAGE analysis of catalase activity of intact scz-IgG<sub>mix</sub> (<b>D</b>) as well as separated H, L chains and their L<sub>n</sub>H<sub>n</sub> oligomers (<b>F</b>) in non-reducing SDS-PAGE gradient 4–15% scz-IgG<sub>mix</sub> before (<b>D</b>) and after treatment of IgGs with DTT (<b>F</b>); panel <b>F</b> corresponds to lane 2 of Panel <b>E</b>. The relative catalase activity (RA, A<sub>240</sub>/min) was revealed using the extracts of 2-3-mm many fragments of one longitudinal slice of the gel corresponding IgGs before (<b>D</b>) and after treatment with DTT (<b>F</b>). The control longitudinal slices of the same gels were stained with Coomassie R250 (<b>E</b>): lane 1 corresponds to intact IgG<sub>mix</sub>, lane 2 to IgG<sub>mix</sub> incubated with 40 mM DTT for 10 min at 30°C, lane 3 to IgG<sub>mix</sub> boiled with DTT. Lane C (<b>E</b>) shows the positions of molecular mass standard markers. The relative activity of F(ab) and F(ab)<sub>2</sub> fragments of individual IgG(4), IgG(12), and IgG(14) (<b>G</b>). The average error of the initial rate determination from two experiments did not exceed 10–15%. For details, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0183867#sec010" target="_blank">Materials and methods</a>.</p>