title: cDNA cloning and expression of potato polyphenol oxidase.
abstract: Polyphenol oxidases (PPOs) of plants are copper metalloproteins which catalyze the oxidation of mono- and o-diphenols to o-diquinones. Although PPOs are believed to be primarily responsible for the deleterious browning of many fruit and vegetable crops and are thought to be involved in plant-pest interactions, direct evidence for these roles is lacking. We report the cloning of two PPO cDNAs from Solanum tuberosum leaves. These cDNAs exhibit 97% and 98% sequence similarity at the DNA and deduced amino acid levels, respectively. Putative copper-binding regions of both cDNAs are very similar to those of mammalian, bacterial and Neurospora tyrosinases. Both leaf PPO cDNAs appear to encode polypeptides which are processed to a mature molecular weight of 57,000. In potato leaves, petioles, roots, and flowers, PPO is encoded by ca. 2 kb transcripts. Leaf PPO mRNA is developmentally regulated and only detectable in young foliage. In contrast, the protein profile of immunologically detectable PPO remains constant from the apical node through the eleventh leaf node.
authors.affiliation: Department of Plant Breeding and Biometry, Cornell University, Ithaca, NY 14853.
authors.forename: M D
authors.initials: MD
authors.lastname: Hunt
authors.forename: N T
authors.initials: NT
authors.lastname: Eannetta
authors.forename: H
authors.initials: H
authors.lastname: Yu
authors.forename: S M
authors.initials: SM
authors.lastname: Newman
authors.forename: J C
authors.initials: JC
authors.lastname: Steffens
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004156:Catechol Oxidase / Q000235:genetics*; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D007527:Isoenzymes / Q000235:genetics*; D008667:Metalloproteins / Q000235:genetics; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000235:genetics; D010944:Plants / Q000201:enzymology / Q000235:genetics; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D007527:Isoenzymes; D008667:Metalloproteins; D012313:RNA; D004247:DNA; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase