A cDNA clone (SAP1) encoding a peroxidase was isolated from a spinach cDNA library using monoclonal antibodies raised against Euglena ascorbate peroxidase. The deduced amino acid sequence of SAP1 had higher homology with the cytosolic ascorbate peroxidases from plant sources than with bacterial peroxidases and classical plant peroxidases. The peroxidase activity of recombinant SAP1 protein expressed in E. coli was 1.6-fold higher with ascorbate than with guaiacol, which was similar to those of endogenous cytosolic ascorbate peroxidases. Here we conclude that SAP1 belongs to new type of ascorbate peroxidase from spinach.
