The peroxidase activity of Cygb with an intramolecular disulfide bond (WT, native), with reduced thiols (Cygb, 5mM DTT), with NEM-blocked thiols (Cygb, NEM), or a mutant Cygb without cysteine groups (Cygb, C38S/C83S) was studied using Amplex red as substrate. The reaction was monitored in the absence of lipids or in the presence of OA or anionic phospholids (DOPA, TOCL, PIP2, PIP3). 0.5 μM Cygb was incubated with 12.5 μM of each lipid.