Identification of horseradisch peroxidases from the Armoracia rusticana transcriptome

Horseradish peroxidases (HRPs) from Armoracia rusticana have long been utilized as reporters in various diagnostic assays and histochemical stainings. Due to lacking sequence information of natural isoenzymes, commercially available HRP is still extracted as a mixture of isoenzymes from the roots of A. rusticana. To elucidate the sequences of the HRP isoforms, the transcriptome of wild horseradish (A. rusticana) based on a pool of root, sprout, stem and leave mRNA was sequenced with 454 FLX technology. Putative HRP transcripts were identified with a novel computational pipeline, expressed in Pichia pastoris and their peroxidase activity tested.