PEROXIDASE FROM STRAWBERRY FRUIT (FRAGARIA ANANASSA-DUCH) - PARTIAL-PURIFICATION AND DETERMINATION OF SOME PROPERTIES

In this work, peroxidase from strawberry fruit was detected, partially purified, and characterized. The total enzyme extract (both soluble a nd associated to membranes) was partially purified by means of (NH4)(2 )SO4 precipitation, molecular exclusion chromatography, and cationic e xchange chromatography. The purification grade achieved was near 35. E ffects of temperature and pH, stability against pH, and thermal stabil ity were analyzed on both crude and partially purified extracts. The m aximum enzyme activity was observed at 30 degrees C and pH 6.0. The en zyme showed low thermal stability and maintained activities equal to o r greater than 50% of its maximum value in the 4-11 pH range. Two pero xidase isoenzymes were detected in strawberry fruit; they were of the basic type (isoelectric points 9.5-10.0) and had molecular masses of 5 8.1 and 65.5 kDa. Strawberry fruit peroxidase activity decreased remar kably as the fruit ripened and was found primarily in a membrane-bound form. Maximum specific activities were found at the ''small green'' a nd ''large green'' ripening stages.