IDENTIFICATION OF ASCORBATE AND GUAIACOL PEROXIDASES IN NEEDLE CHLOROPLASTS OF SPRUCE TREES

We present evidence of two peroxidases in needle chloroplasts of spruc e (Picea abies L. cv. Karsten) trees. One of these uses ascorbate (EC 1.11.1.11) and the other uses guaiacol (EC 1.11.1.7) as the electron d onor. In some cases, two chloroplast guaiacol isozymes were detected. In total needle extract, in addition to the above-mentioned peroxidase s, two ascorbate peroxidase and four guaiacol peroxidase isozymes were found. A rapid isolation procedure was developed for the purification of the chloroplast guaiacol peroxidase. The native molecule has a mol ecular mass of 158 kDa and consists of four monomers of 41 kDa. The pI of the enzyme was found to be 4.4 by isoelectric focusing on an ultra thin polyacrylamide gel. The enzyme has a broad pH activity spectrum f rom 5 to 6.8 and an optimum temperature of 55C. Concanavalin A affinit y chromatography, periodate oxidation, trypsin digestion and a thermal stability study suggest that this enzyme is glycosylated.