Nonphotosynthetic plastids are important sites for the biosynthesis of starch, fatty acids, and assimilation nitrogen into amino acids in a wide range plant tissues. Unlike chloroplasts, all metabolites these processes have to be imported, or generated by oxidative metabolism within organelle. The aim this review is summarize our present understanding anabolic pathways involved, requirement import precursors from cytosol, provision energy biosynthesis, interaction between that share common...

Protein phosphorylation in amyloplasts and chloroplasts of Triticum aestivum (wheat) was investigated after the incubation intact plastids with γ-32P-ATP. Among soluble phosphoproteins detected plastids, three forms starch branching enzyme (SBE) were phosphorylated (SBEI, SBEIIa, SBEIIb), both SBE (SBEI SBEIIa) shown to be sequencing immunoprecipitated 32P-labeled using quadrupole-orthogonal acceleration time flight mass spectrometry. Phosphoamino acid analysis indicated that proteins are...

Abstract Protein-protein interactions among enzymes of amylopectin biosynthesis were investigated in developing wheat (Triticum aestivum) endosperm. Physical between starch branching (SBEs) and synthases (SSs) identified from endosperm amyloplasts during the active phase deposition grain using immunoprecipitation cross-linking strategies. Coimmunoprecipitation experiments peptide-specific antibodies indicate that at least two distinct complexes exist containing SSI, SSIIa, either SBEIIa or...

Mutations affecting specific starch biosynthetic enzymes commonly have pleiotropic effects on other in the same metabolic pathway. Such genetic evidence indicates functional relationships between components of system, including synthases (SSs), branching (BEs), and debranching enzymes; however, molecular explanation for these interactions is not known. One possibility that SSs, BEs, and/or associate physically with each multisubunit complexes. To test this hypothesis, study sought to...

The amylose extender (ae–) mutant of maize lacks starch branching enzyme IIb (SBEIIb) activity, resulting in amylopectin with reduced branch point frequency, and longer glucan chains. Recent studies indicate isozymes soluble synthases form high molecular weight complexes SBEII isoforms. This study investigated the effect loss SBEIIb activity on interactions between biosynthetic enzymes endosperm amyloplasts. Results show distinct patterns protein–protein amyloplasts ae– mutants compared wild...

Amylopectin is a highly branched, organized cluster of glucose polymers, and the major component rice starch. Synthesis amylopectin requires fine co-ordination between elongation polymers by soluble starch synthases (SSs), generation branches branching enzymes (BEs), removal misplaced debranching (DBEs). Among various isozymes having role in biosynthesis, limited numbers SS BE have been demonstrated to interact via protein-protein interactions maize wheat amyloplasts. This study investigated...

amylose extender (ae−) starches characteristically have modified starch granule morphology resulting from amylopectin with reduced branch frequency and longer glucan chains in clusters, caused by the loss of activity major branching enzyme (SBE), which maize endosperm is SBEIIb. A recent study ae− lacking SBEIIb protein (termed ae1.1 herein) showed that novel protein–protein interactions between enzymes biosynthesis amyloplast could explain phenotype mutant. The present examined an allelic...

Summary Purified pea root plastids were supplied with glutamine, 2‐oxoglutarate and phosphorylated sugars. Formation of glutamate was linear for 75 min dependent upon the intactness organelle. Glucose‐6‐phosphate ribose‐5‐phosphate most effective substrates in supporting synthesis. Flux through oxidative pentose phosphate pathway during synthesis purified followed by monitoring release 14 CO 2 from [1‐ C]glucose‐6‐phosphate. evolution C‐1 presence both glutamine could be inhibited...

ABSTRACT In this study, the functional properties of A‐ and B‐type wheat starch granules from two commercial flours were investigated for digestibility in vitro, chemical composition (e.g., amylose, protein, ash content), gelatinization, retrogradation, pasting properties. The branch chain length distribution these also determined using high‐performance anion exchange chromatography (HPAEC). Wheat starches with different granular sizes not only had degrees enzymatic hydrolysis thermal...

The sugary-2 mutation in maize (Zea mays L.) is a result of the loss catalytic activity endosperm-specific SS (starch synthase) IIa isoform causing major alterations to amylopectin architecture. present study reports biochemical and molecular analysis an allelic variant expressing catalytically inactive form SSIIa sheds new light on its central role protein-protein interactions determination starch granule proteome. mutant revealed two amino acid substitutions, one being highly conserved...

The starch-rich endosperms of the Poaceae, which includes wild grasses and their domesticated descendents cereals, have provided humankind livestock with bulk daily calories since dawn civilization up to present day. There are currently unprecedented pressures on global food supplies, largely resulting from population growth, loss agricultural land that is linked increased urbanization, climate change. Since cereal yields essentially underpin world feed supply, it critical we understand...

Plastids in non-photosynthetic tissue are the site of fatty acid, starch and amino acid synthesis. The intermediates to support these activities imported from cytoplasm or generated by carbohydrate oxidation within organelle. This review considers current understanding nature substrates which transported into such plastids, interaction between pathways organelle have a supply demand relationship, potentially compete for substrates.

The subcellular distribution of enzymes the oxidative pentose phosphate pathway was studied in plants. Root and leaf tissues from several species were separated by differential centrifugation into plastidic cytosolic fractions. In all studied, glucose 6-phosphate dehydrogenase 6-phosphogluconate found both compartments. maize pea root, spinach leaf, non-oxidative (transaldolase, transketolase, ribose 5-phosphate isomerase, ribulose 3-epimerase) appear to be restricted plastid. tobacco root...

SUMMARY Sphagnum cuspidatum Ehrh. ex. Hoffm. was removed from a relatively remote moorland site at the Migneint, N. Wales and Holme Moss, S. Pennines — that has been subjected to atmospheric pollution deposition for period of least last 200 yr. When exposed elevated ammonium (NH 4 + ) concentrations (0·1 1·0 mM) under laboratory conditions 30 d, showed marked reduction in growth, whereas Pennine population, growth stimulated above untreated control tissue both 0·1 mM NH . The largest...

In roots, nitrate assimilation is dependent upon a supply of reductant that initially generated by oxidative metabolism including the pentose phosphate pathway (OPPP). The uptake nitrite into plastids and its subsequent reduction reductase (NiR) glutamate synthase (GOGAT) are potentially important control points may affect assimilation. To support operation OPPP there need for glucose 6-phosphate (Glc6P) to be imported translocator (GPT). Competitive inhibitors Glc6P had little impact on...