SDS-PAGE analysis of CotA purification. Samples from cell free extracts (CFE), heat incubation (HI), anion exchange chromatography (AEC) and size exclusion chromatography (SEC) were denatured for 20 min at 95°C in SDS loading buffer containing β-mercapthoethanol. Sample SEC* was incubated for 5 min at 95° in SDS loading buffer containing β-mercapthoethanol. M, marker. Specific activity was determined using the standard ABTS oxidation assay.