ISOLATION, PURIFICATION, AND SUBCELLULAR-LOCALIZATION OF ISOZYMES OF SUPEROXIDE-DISMUTASE FROM SCOTS PINE (PINUS-SYLVESTRIS L) NEEDLES

• Two of four isozymes of superoxide dismutase (SOD) (EC 1.15.1.1) were purified from Scots pine (Pinus sylvestris L.) needles. One form was cytosolic (SOD-1) and the other was associated with chloroplasts (SOD-3). The holoenzyme molecular masses was estimated at approximately 35 kilodaltons by gel filtration. The subunit molecular weight of the dimeric enzymes was estimated to 16.5 kilodaltons (SOD-1) and 20.4 kilodaltons (SOD-3) on sodium dodecyl sulfatepolyacrylamide gels. The NH2-terminal sequence of the pine enzymes showed similarities to other purified superoxide dismutases located in the corresponding compartment. The cytosolic form revealed two additional amino acids at position 1 and 2 at the NH2-terminal. Both forms were cyanide- and hydrogenperoxide-sensitive and SOD-3 was found to contain approximately one copper atom per subunit, indicating that they belong to the cupro-zinc SODs. The isoelectric point was 4.9 and 4.5 for SOD-1 and SOD-3, respectively.

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