CHLOROPEROXIDASE, A PEROXIDASE WITH POTENTIAL

Chloroperoxidase is an extracellular heme glycoprotein produced by the imperfect fungus Caldariomyces fumago. The enzyme can catalyse chlorination reactions as well as act as a catalase or a peroxidase. As a peroxidase, it has a wide substrate specificity and we are interested in some applied aspects of this activity, requiring the production and purification of moderate quantities of the enzyme. High levels of chloroperoxidase are produced in a fructose synthetic medium, and highest enzyme production occurs in a low-shear environment. Fungal pellets produce enzyme continuously at low medium replacement rates and at up to 0.6 g enzyme per 1: chloroperoxidase is essentially the only extracellular enzyme produced. Enzyme purification is uncomplicated and gives good yields of high purity. Pure enzyme is stable for weeks at room temperature and under pH control. Chloroperoxidase can be ionically bound to aminopropyl glass, then covalently immobilized by glutaraldehyde crosslinking. Immobilized preparations have been washed and re-used five times, and are most stable at pH 5.5-6. Like many peroxidases, chloroperoxidase will oxidize phenols and phenolics, often causing a precipitate, and can totally remove phenols at low aqueous concentrations. Chloroperoxidase incubation with the petroporphyrin component of crude oil asphaltene (fraction 5) causes a reduction or removal of the Soret band (410 nm) and the alpha-peak (573 nm). This petroporphyrin fraction is enriched with vanadium which poisons the chemical catalyst used in cracking crude oil.