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Updated: Oct 4, 2026
Identification of Plant Ice-binding Proteins Through Assessment of Ice-recrystallization Inhibition and Isolation Using Ice-affinity Purification
Published on: May 5, 2017
Evidence for a tetrameric form of iceberg lettuce (Lactuca sativa L.) polyphenol oxidase: purification and
S Chazarra1, F García-Carmona, J Cabanes
1Departamento de Bioquímica y Biología Molecular A, Edificio de Veterinaria, Unidad docente de Biología, Universidad de Murcia, Campus de Espinardo, 30071, Murcia, Spain.
Abstract:
Polyphenol oxidase from iceberg lettuce (Lactuca sativa L.) chloroplasts was released from the thylakoid-membrane by sonication, and it was extensively purified to homogeneity as judged by SDS-PAGE. Purification was achieved by ammonium sulfate fractionation, gel-filtration chromatography, and ion-exchange chromatography. Two molecular forms were separated by gel-filtration chromatography with apparent molecular masses of 188 and 49 kDa. Both forms were characterized by sedimentation analysis with S(20,W) values of 10.2 and 4.1 S, respectively. For the high-molecular-weight form purified to homogeneity, denaturing SDS-PAGE indicated a molecular mass of 60 kDa. Thus, from these data we suggest that lettuce polyphenol oxidase is a tetramer of identical subunits.