Purification and characterisation of two acidic peroxidase isoforms from the sheaths of bamboo shoots

Three isoforms of peroxidase (POD) were isolated from the sheaths of bamboo shoots by chromatofocusing on Polybuffer exchanger PBE 94. POD-A was partially purified, and POD-B and POD-C were purified and characterised. POD-A was a basic peroxidase, whereas POD-B and POD-C were acidic peroxidases with different isoelectric points. Using o-phenylenediamine (OPD) as a hydrogen-donor, the optimum temperatures for function of POD-B and POD-C were 55 and 45-55 degrees C, respectively, while both had the same optimum pH of 4.5. Both isoforms were stable between 30 and 60 degrees C and between pH 4.5 and 10. The activities of the POD isoforms towards hydrogen-donors were both pH and concentration dependent. Under optimal conditions, POD-B and POD-C catalysed the oxidation of catechol, pyrogallol, and OPD at higher rates than guaiacol, o-dianisidine and 2, 2-azino-bis- (3-ethylbenzothiazoline-6-sulphonic acid). Both isoforms were almost completely inhibited by chemical modification reagent diethyl pyrocarbonate (4.5 mM).