title: The bacterial-type phosphoenolpyruvate carboxylase isozyme from developing castor oil seeds is subject to in vivo regulatory phosphorylation at serine-451.
abstract: Phosphoenolpyruvate carboxylase (PEPC) is a tightly controlled anaplerotic enzyme situated at a pivotal branch point of plant carbohydrate-metabolism. In developing castor oil seeds (COS) a novel allosterically-densensitized 910-kDa Class-2 PEPC hetero-octameric complex arises from a tight interaction between 107-kDa plant-type PEPC and 118-kDa bacterial-type PEPC (BTPC) subunits. Mass spectrometry and immunoblotting with anti-phosphoSer451 specific antibodies established that COS BTPC is in vivo phosphorylated at Ser451, a highly conserved target residue that occurs within an intrinsically disordered region. This phosphorylation was enhanced during COS development or in response to depodding. Kinetic characterization of a phosphomimetic (S451D) mutant indicated that Ser451 phosphorylation inhibits the catalytic activity of BTPC subunits within the Class-2 PEPC complex.
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors.forename: Katie J
authors.initials: KJ
authors.lastname: Dalziel
authors.forename: Brendan
authors.initials: B
authors.lastname: O'Leary
authors.forename: Carolyne
authors.initials: C
authors.lastname: Brikis
authors.forename: Srinath K
authors.initials: SK
authors.lastname: Rao
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: She
authors.forename: Terry
authors.initials: T
authors.lastname: Cyr
authors.forename: William C
authors.initials: WC
authors.lastname: Plaxton
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D045163:Antibodies, Phospho-Specific; D002368:Castor Oil / Q000737:chemistry; D005511:Food Handling; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012278:Ricinus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D012639:Seeds / Q000201:enzymology* / Q000254:growth & development; D016415:Sequence Alignment; D012694:Serine / Q000378:metabolism*
chemical_list: D045163:Antibodies, Phospho-Specific; D007527:Isoenzymes; D050505:Mutant Proteins; D010940:Plant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D012694:Serine; D002368:Castor Oil; D010730:Phosphoenolpyruvate Carboxylase