The bacterial-type phosphoenolpyruvate carboxylase isozyme from developing castor oil seeds is subject to in vivo regulatory phosphorylation at serine-451.

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.

Tissue-specific expression and post-translational modifications of plant- and bacterial-type phosphoenolpyruvate carboxylase isozymes of the castor oil plant, Ricinus communis L.

This study employs transcript profiling together with immunoblotting and co-immunopurification to assess the tissue-specific expression, protein:protein interactions, and post-translational modifications (PTMs) of plant- and bacterial-type phosphoenolpyruvate carboxylase (PEPC) isozymes (PTPC and BTPC, respectively) in the castor plant, Ricinus communis. Previous studies established that the Class-1 PEPC (PTPC homotetramer) of castor oil seeds (COS) is activated by phosphorylation at Ser-11 and inhibited by monoubiquitination at Lys-628 during endosperm development and germination, respectively. Elimination of photosynthate supply to developing COS by depodding caused the PTPC of the endosperm and cotyledon to be dephosphorylated, and then subsequently monoubiquitinated in vivo.

Phosphorylation of bacterial-type phosphoenolpyruvate carboxylase at Ser425 provides a further tier of enzyme control in developing castor oil seeds.

PEPC [PEP (phosphoenolpyruvate) carboxylase] is a tightly controlled anaplerotic enzyme situated at a pivotal branch point of plant carbohydrate metabolism. Two distinct oligomeric PEPC classes were discovered in developing COS (castor oil seeds). Class-1 PEPC is a typical homotetramer of 107 kDa PTPC (plant-type PEPC) subunits, whereas the novel 910-kDa Class-2 PEPC hetero-octamer arises from a tight interaction between Class-1 PEPC and 118 kDa BTPC (bacterial-type PEPC) subunits.

Bacterial-type phosphoenolpyruvate carboxylase (PEPC) functions as a catalytic and regulatory subunit of the novel class-2 PEPC complex of vascular plants.

Phosphoenolpyruvate carboxylase (PEPC) is a tightly regulated anaplerotic enzyme situated at a major branch point of the plant C metabolism. Two distinct oligomeric classes of PEPC occur in the triglyceride-rich endosperm of developing castor oil seeds (COS). Class-1 PEPC is a typical homotetramer composed of identical 107-kDa plant-type PEPC (PTPC) subunits (encoded by RcPpc3), whereas the novel Class-2 PEPC 910-kDa hetero-octameric complex arises from a tight interaction between Class-1 PEPC and distantly related 118-kDa bacterial-type PEPC (BTPC) polypeptides (encoded by RcPpc4).

Characterization of the NADP malic enzyme gene family in the facultative, single-cell C4 monocot Hydrilla verticillata.

Hydrilla verticillata has a facultative single-cell system that changes from C3 to C4 photosynthesis. A NADP+-dependent malic enzyme (NADP-ME) provides a high [CO2] for Rubisco fixation in the C4 leaf chloroplasts. Of three NADP-ME genes identified, only hvme1 was up-regulated in the C4 leaf, during the light period, and it possessed a putative transit peptide.

Identification of C4 responsive genes in the facultative C4 plant Hydrilla verticillata.

The aquatic monocot Hydrilla verticillata (L.f.) Royle is a well-documented facultative C4 NADP-malic enzyme species in which the C4 and Calvin cycles operate in the same cell with the specific carboxylases confined to the cytosol and chloroplast, respectively.

Photosynthetic and other phosphoenolpyruvate carboxylase isoforms in the single-cell, facultative C(4) system of Hydrilla verticillata.

The submersed monocot Hydrilla verticillata (L.f.) Royle is a facultative C(4) plant.

C4 mechanisms in aquatic angiosperms: comparisons with terrestrial C4 systems.

Aquatic C4 photosynthesis probably arose in response to dissolved CO2 limitations, possibly before its advent in terrestrial plants. Of over 7600 C4 species, only about a dozen aquatic species are identified. Amphibious Eleocharis species (sedges) have C3-C4 photosynthesis and Kranz anatomy in aerial, but not submersed, leaves.