Phospholipids are hydrolysed by phospholipase D and the liberated
choline is subsequently oxidized by choline oxidase (CHO) to betaine
with the simultaneous production of hydrogen peroxide. In the
presence of peroxidase (POD) the hydrogen peroxide couples
oxidatively the 4 – Aminophenazone (4-AP) and dichlorophenol to
forms a quinonemine dye