title: Dual specificities of the glyoxysomal/peroxisomal processing protease Deg15 in higher plants.
abstract: Glyoxysomes are a subclass of peroxisomes involved in lipid mobilization. Two distinct peroxisomal targeting signals (PTSs), the C-terminal PTS1 and the N-terminal PTS2, are defined. Processing of the PTS2 on protein import is conserved in higher eukaryotes. The cleavage site typically contains a Cys at P1 or P2. We purified the glyoxysomal processing protease (GPP) from the fat-storing cotyledons of watermelon (Citrullus vulgaris) by column chromatography, preparative native isoelectric focusing, and 2D PAGE. The GPP appears in two forms, a 72-kDa monomer and a 144-kDa dimer, which are in equilibrium with one another. The equilibrium is shifted on Ca(2+) removal toward the monomer and on Ca(2+) addition toward the dimer. The monomer is a general degrading protease and is activated by denatured proteins. The dimer constitutes the processing protease because the substrate specificity proven for the monomer (Phi-Arg/Lys downward arrow) is different from the processing substrate specificity (Cys-Xxx downward arrow/Xxx-Cys downward arrow) found with the mixture of monomer and dimer. The Arabidopsis genome analysis disclosed three proteases predicted to be in peroxisomes, a Deg-protease, a pitrilysin-like metallopeptidase, and a Lon-protease. Specific antibodies against the peroxisomal Deg-protease from Arabidopsis (Deg15) identify the watermelon GPP as a Deg15. A knockout mutation in the DEG15 gene of Arabidopsis (At1g28320) prevents processing of the glyoxysomal malate dehydrogenase precursor to the mature form. Thus, the GPP/Deg15 belongs to a group of trypsin-like serine proteases with Escherichia coli DegP as a prototype. Nevertheless, the GPP/Deg15 possesses specific characteristics and is therefore a new subgroup within the Deg proteases.
authors.affiliation: Lehrstuhl für Botanik, Technische Universität München, Wissenschaftszentrum Weihenstephan, D-85350 Freising, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Helm
authors.forename: Carsten
authors.initials: C
authors.lastname: Lück
authors.forename: Jakob
authors.initials: J
authors.lastname: Prestele
authors.forename: Georg
authors.initials: G
authors.lastname: Hierl
authors.forename: Pitter F
authors.initials: PF
authors.lastname: Huesgen
authors.forename: Thomas
authors.initials: T
authors.lastname: Fröhlich
authors.forename: Georg J
authors.initials: GJ
authors.lastname: Arnold
authors.forename: Iwona
authors.initials: I
authors.lastname: Adamska
authors.forename: Angelika
authors.initials: A
authors.lastname: Görg
authors.forename: Friedrich
authors.initials: F
authors.lastname: Lottspeich
authors.forename: Christine
authors.initials: C
authors.lastname: Gietl
mesh_terms: D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029773:Citrullus / Q000201:enzymology*; D004792:Enzyme Precursors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020676:Glyoxysomes / Q000201:enzymology* / Q000235:genetics; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D008291:Malate Dehydrogenase / Q000235:genetics; D009154:Mutation; D033903:Periplasmic Proteins / Q000737:chemistry / Q000378:metabolism*; D020675:Peroxisomes / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011499:Protein Processing, Post-Translational; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D013379:Substrate Specificity / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D004792:Enzyme Precursors; D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; D010940:Plant Proteins; D008291:Malate Dehydrogenase; C522900:Deg15 protein, Arabidopsis; C061682:DegP protease; D012697:Serine Endopeptidases