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Ethanolamine Metabolism in Plant Tissues 总被引:3,自引:2,他引:1
Ethanolamine is readily metabolized by oat, pea, wheat, apple and carrot tissue preparations. Ethanolamine-1,2 (14)C was incorporated into the lipid fraction, and (14)C activity was distributed in the organic acid, sugar, acid volatile, carbon dioxide and insoluble residue fractions. The distribution varied with the particular tissue. Incorporation into the lipid fraction occurred in tissue homogenates in the absence of ATP by a Ca(++) activated system similar to that reported for animal preparations. The initial step in ethanolamine oxidation involves an amine oxidase. Glycolaldehyde and glyoxylic acid are metabolic intermediates, the former in the conversion of ethanolamine to carbon dioxide. No evidence was obtained for the operation of an ethanolamine transaminase or for the involvement of phosphorylated intermediates in the conversion of ethanolamine to carbon dioxide. 相似文献
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Posttranslational modifications (PTMs) of proteins greatly expand proteome diversity, increase functionality, and allow for rapid responses, all at relatively low costs for the cell. PTMs play key roles in plants through their impact on signaling, gene expression, protein stability and interactions, and enzyme kinetics. Following a brief discussion of the experimental and bioinformatics challenges of PTM identification, localization, and quantification (occupancy), a concise overview is provided of the major PTMs and their (potential) functional consequences in plants, with emphasis on plant metabolism. Classic examples that illustrate the regulation of plant metabolic enzymes and pathways by PTMs and their cross talk are summarized. Recent large-scale proteomics studies mapped many PTMs to a wide range of metabolic functions. Unraveling of the PTM code, i.e. a predictive understanding of the (combinatorial) consequences of PTMs, is needed to convert this growing wealth of data into an understanding of plant metabolic regulation.The primary amino acid sequence of proteins is defined by the translated mRNA, often followed by N- or C-terminal cleavages for preprocessing, maturation, and/or activation. Proteins can undergo further reversible or irreversible posttranslational modifications (PTMs) of specific amino acid residues. Proteins are directly responsible for the production of plant metabolites because they act as enzymes or as regulators of enzymes. Ultimately, most proteins in a plant cell can affect plant metabolism (e.g. through effects on plant gene expression, cell fate and development, structural support, transport, etc.). Many metabolic enzymes and their regulators undergo a variety of PTMs, possibly resulting in changes in oligomeric state, stabilization/degradation, and (de)activation (Huber and Hardin, 2004), and PTMs can facilitate the optimization of metabolic flux. However, the direct in vivo consequence of a PTM on a metabolic enzyme or pathway is frequently not very clear, in part because it requires measurements of input and output of the reactions, including flux through the enzyme or pathway. This Update will start out with a short overview on the major PTMs observed for each amino acid residue (PTMs, including determination of the localization within proteins (i.e. the specific residues) and occupancy. Challenges in dealing with multiple PTMs per protein and cross talk between PTMs will be briefly outlined. We then describe the major physiological PTMs observed in plants as well as PTMs that are nonenzymatically induced during sample preparation (PTMs, in particular for enzymes in primary metabolism (Calvin cycle, glycolysis, and respiration) and the C4 shuttle accommodating photosynthesis in C4 plants (PTMs observed in plants
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Open in a separate windowThere are many recent reviews focusing on specific PTMs in plant biology, many of which are cited in this Update. However, the last general review on plant PTMs is from 2010 (Ytterberg and Jensen, 2010); given the enormous progress in PTM research in plants over the last 5 years, a comprehensive overview is overdue. Finally, this Update does not review allosteric regulation by metabolites or other types of metabolic feedback and flux control, even if this is extremely important in the regulation of metabolism and (de)activation of enzymes. Recent reviews for specific pathways, such as isoprenoid metabolism (Kötting et al., 2010; Banerjee and Sharkey, 2014; Rodríguez-Concepción and Boronat, 2015), tetrapyrrole metabolism (Brzezowski et al., 2015), the Calvin-Benson cycle (Michelet et al., 2013), starch metabolism (Kötting et al., 2010; Geigenberger, 2011; Tetlow and Emes, 2014), and photorespiration (Hodges et al., 2013) provide more in-depth discussions of metabolic regulation through various posttranslational mechanisms. Many of the PTMs that have been discovered in the last decade through large-scale proteomics approaches have not yet been integrated in such pathway-specific reviews, because these data are not always easily accessible and because the biological significance of many PTMs is simply not yet understood. We hope that this Update will increase the general awareness of the existence of these PTM data sets, such that their biological significance can be tested and incorporated in metabolic pathways. 相似文献
Amino Acid Residue | Observed Physiological PTM in Plants | PTMs Caused by Sample Preparation |
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Ala (A) | Not known | |
Arg (R) | Methylation, carbonylation | |
Asn (N) | Deamidation, N-linked gycosylation | Deamidation |
Asp (D) | Phosphorylation (in two-component system) | |
Cys (C) | Glutathionylation (SSG), disulfide bonded (S-S), sulfenylation (-SOH), sulfonylation (-SO3H), acylation, lipidation, acetylation, nitrosylation (SNO), methylation, palmitoylation, phosphorylation (rare) | Propionamide |
Glu (E) | Carboxylation, methylation | Pyro-Glu |
Gln (Q) | Deamidation | Deamidation, pyro-Glu |
Gly (G) | N-Myristoylation (N-terminal Gly residue) | |
His (H) | Phosphorylation (infrequent) | Oxidation |
Ile (I) | Not known | |
Leu (L) | Not known | |
Lys (K) | N-ε-Acetylation, methylation, hydroxylation, ubiquitination, sumoylation, deamination, O-glycosylation, carbamylation, carbonylation, formylation | |
Met (M) | (De)formylation, excision (NME), (reversible) oxidation, sulfonation (-SO2), sulfoxation (-SO) | Oxidation, 2-oxidation, formylation, carbamylation |
Phe (F) | Not known | |
Pro (P) | Carbonylation | Oxidation |
Ser (S) | Phosphorylation, O-linked glycosylation, O-linked GlcNAc (O-GlcNAc) | Formylation |
Thr (T) | Phosphorylation, O-linked glycosylation, O-linked GlcNAc (O-GlcNAc), carbonylation | Formylation |
Trp (W) | Glycosylation (C-mannosylation) | Oxidation |
Tyr (Y) | Phosphorylation, nitration | |
Val (V) | Not known | |
Free NH2 of protein N termini | Preprotein processing, Met excision, formylation, pyro-Glu, N-myristoylation, N-acylation (i.e. palmitoylation), N-terminal α-amine acetylation, ubiquitination | Formylation (Met), pyro-Glu (Gln) |
Table II.
Most significant and/or frequent PTMs observed in plantsType of PTM (Reversible, Except if Marked with an Asterisk) | Spontaneous (S; Nonenzymatic) or Enzymatic (E) | Comment on Subcellular Location and Frequency |
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Phosphorylation (Ser, Thr, Tyr, His, Asp) | E | His and Asp phosphorylation have low frequency |
S-Nitrosylation (Cys) and nitration* (Tyr) | S (RNS), but reversal is enzymatic for Cys by thioredoxins | Throughout the cell |
Acetylation (N-terminal α-amine, Lys ε-amine) | E | In mitochondria, very little N-terminal acetylation, but high Lys acetylation; Lys acetylation correlates to [acetyl-CoA] |
Deamidation (Gln, Asn) | S, but reversal of isoAsp is enzymatic by isoAsp methyltransferase | Throughout the cell |
Lipidation (S-acetylation, N-meristoylation*, prenylation*; Cys, Gly, Lys, Trp, N terminal) | E | Not (or rarely) within plastids, mitochondria, peroxisomes |
N-Linked glycosylation (Asp); O linked (Lys, Ser, Thr, Trp) | E | Only proteins passing through the secretory system; O linked in the cell wall |
Ubiquination (Lys, N terminal) | E | Not within plastids, mitochondria, peroxisomes |
Sumoylation (Lys) | E | Not within plastids, mitochondria, peroxisomes |
Carbonylation* (Pro, Lys, Arg, Thr) | S (ROS) | High levels in mitochondria and chloroplast |
Methylation (Arg, Lys, N terminal) | E | Histones (nucleus) and chloroplasts; still underexplored |
Glutathionylation (Cys) | E | High levels in chloroplasts |
Oxidation (Met, Cys) | S (ROS) and E (by PCOs; see Fig. 1B), but reversal is enzymatic by Met sulfoxide reductases, glutaredoxins, and thioredoxins, except if double oxidized | High levels in mitochondria and chloroplast |
Peptidase* (cleavage peptidyl bond) | E | Throughout the cell |
S-Guanylation (Cys) | S (RNS) | Rare; 8-nitro-cGMP is signaling molecule in guard cells |
Formylation (Met) | S, but deformylation is enzymatic by peptide deformylase | All chloroplasts and mitochondria-encoded proteins are synthesized with initiating formylated Met |
Table III.
Regulation by PTMs in plant metabolism and classic examples of well-studied enzymes and pathwaysMany of these enzymes also undergo allosteric regulation through cellular metabolites. GAPDH, Glyceraldehyde-3-phosphate dehydrogenase; PRK, phosphoribulokinase.Process | Enzymes | PTMs, Protein Modifiers, Localization | References |
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Calvin-Benson cycle (chloroplasts) | Many enzymes | Oxidoreduction of S-S bonds, reversible nitrosylation, glutathionylation; through ferredoxin/ferredoxin-thioredoxin reductase/thioredoxins (mostly f and m) and glutaredoxins; proteomics studies in Arabidopsis and C. reinhardtii | Michelet et al. (2013) |
Rubisco | Methylation, carbamylation, acetylation, N-terminal processing, oligomerization; classical studies in pea (Pisum sativum), spinach (Spinacia oleracea), and Arabidopsis | Houtz and Portis (2003); Houtz et al. (2008) | |
GAPDH/CP12/PRK supercomplex | Dynamic heterooligomerization through reversible S-S bond formation controlled by thioredoxins | Graciet et al. (2004); Michelet et al. (2013); López-Calcagno et al. (2014) | |
Glycolysis | Cytosolic PEPC | Phosphorylation (S, T), monoubiquitination | O’Leary et al. (2011) |
Photorespiration | Seven enzymes are phosphorylated | Phosphorylation from meta-analysis of public phosphoproteomics data for Arabidopsis; located in chloroplasts, peroxisomes, mitochondria | Hodges et al. (2013) |
Maize glycerate kinase | Redox-regulated S-S bond; thioredoxin f; studied extensively in chloroplasts of C4 maize | Bartsch et al. (2010) | |
Respiration (mitochondria) | Potentially many enzymes, but functional/biochemical consequences are relatively unexplored | Recent studies suggested PTMs for many tricarboxylic acid cycle enzymes, including Lys acetylation and thioredoxin-driven S-S formation; in particular, succinate dehydrogenase and fumarase are inactivated by thioredoxins | Lázaro et al. (2013); Schmidtmann et al. (2014); Daloso et al. (2015) |
PDH | Ser (de)phosphorylation by intrinsic kinase and phosphatase; ammonia and pyruvate control PDH kinase activity; see Figure 1B | Thelen et al. (2000); Tovar-Méndez et al. (2003) | |
C4 cycle (C3 and C4 homologs also involved in glycolysis and/or gluconeogenesis) | Pyruvate orthophosphate dikinase | Phosphorylation by pyruvate orthophosphate dikinase-RP, an S/T bifunctional kinase-phosphatase; in chloroplasts | Chastain et al. (2011); Chen et al. (2014) |
PEPC | Phosphorylation; allosteric regulation by malate and Glc-6-P; in cytosol in mesophyll cells in C4 species (e.g. Panicum maximum); see Figure 1A | Izui et al. (2004); Bailey et al. (2007) | |
PEPC kinase | Ubiquitination resulting in degradation (note also diurnal mRNA levels and linkage to activity level; very low protein level); in cytosol in mesophyll cells in C4 species (e.g. Flaveria spp. and maize) | Agetsuma et al. (2005) | |
PEPC kinase | Phosphorylation in cytosol in bundle sheath cells | Bailey et al. (2007) | |
Starch metabolism (chloroplasts) | ADP-Glc pyrophosphorylase | Redox-regulated disulfide bonds and dynamic oligomerization; thioredoxins; see Figure 1C | Geigenberger et al. (2005); Geigenberger (2011) |
Starch-branching enzyme II | Phosphorylation by Ca2+-dependent protein kinase; P-driven heterooligomerization | Grimaud et al. (2008); Tetlow and Emes (2014) | |
Suc metabolism (cytosol) | SPS (synthesis of Suc) | (De)phosphorylation; SPS kinase and SPS phosphatase; 14-3-3 proteins; cytosol (maize and others) | Huber (2007) |
Suc synthase (breakdown of Suc) | Phosphorylation; Ca2+-dependent protein kinase; correlations to activity, localization, and turnover | Duncan and Huber (2007); Fedosejevs et al. (2014) | |
Photosynthetic electron transport (chloroplast thylakoid membranes) | PSII core and light-harvesting complex proteins | (De)phosphorylation by state-transition kinases (STN7/8) and PP2C phosphatases (PBCP and PPH1/TAP38) | Pesaresi et al. (2011); Tikkanen et al. (2012); Rochaix (2014) |
Nitrogen assimilation | Nitrate reductase | (De)phosphorylation; 14-3-3 proteins | Lillo et al. (2004); Huber (2007) |
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JOHN D. KEMP 《Physiologia plantarum》1975,35(1):53-58
Rates of protein synthesis in normal callus tissues (either tight or loose morphological form), in crown gall callus tissues and in cultured pith cells were measured for both the lower surface cells (those in contact with the original growth medium) and upper surface cells (those never in contact with the growth medium until labeling). Cells of both surfaces of loose and crown gall callus and the upper-surface cells of tight callus had similar rates of protein synthesis, 29–31 mg of protein synthesized × (g protein)−1× h−1. The lower surface cells of tight callus had a 35% lower rate of synthesis, 20 mg × g−1× h−1. Pulse-chase experiments suggested that rates of protein degradation for all tissues were the same, 21–23 mg protein × (g protein)−1× h−1. Thus, there probably was no accumulation of protein in the lower surface cells of tight callus tissue, but the other tissues had rates of accumulation equaling 10 mg × (g protein)−1× h−1. Autoradiography and electron-microscopic examination of cells in tight callus labeled with 3H-leucine show that: (a) the lower-surface cells were more degenerate than cells within the callus or on the upper surface; and (b) the first few cell layers nearest the medium were preferentially labeled. Pulse-chase experiments were also used to quantitate the nonprecursor pool (defined as that tritium in the soluble amino acid pool that does not equilibrate with protein during a pulse-chase experiment). The nonprecursor pool increased linearly with time at the same rate as incorporation of 3H-leucine into protein. Furthermore, the nonprecursor pool copurified with leucine and was probably either D- or L-leucine. 相似文献
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植物次生代谢基因工程 总被引:8,自引:0,他引:8
植物次生代谢基因工程,是利用基因工程技术对植物次生代谢途径的遗传特性进行改造,进而改变植物次生代谢产物。植物次生代谢基因工程的出现是人类对次生代谢途径的深入了解和分子生物学向纵深发展的结果,同时它又促进了次生代谢分子生物学的发展。调控因子的应用和多基因的协同转化为植物次生代谢基因工程拓宽了思路。从次生代谢图谱、植物基因工程策略和植物转基因方法等方面对植物次生代谢的基因工程研究进展做一简要概述。 相似文献
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Treatment of Ricinus communis seeds with GA accelerated the production of reducing sugars and increased the total carbohydrate content. The effect increased progressively with increasing concentration of GA. — GA treatment also induced an earlier appearance of starch which was shown to be completely absent at the early stages of germination. Furthermore, GA accelerated the conversion of oils into carbohydrates. — Analysis of germinating seeds for their nitrogen content showed that whenever an increase in soluble-N due to GA treatment was detected, there was a decrease in protein-N. Breakdown of protein and formation of soluble-N increased progressively with increase in GA concentration. — GA induced variable changes in the length of the radicles and the hypocotyls, the dry weight and the water content of germinating seeds. 相似文献
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Pyrimidine Metabolism in Lemna minor: I. Functional Compartmentation of Chloroplast Pyrimidine Metabolism in a Higher Plant 下载免费PDF全文
Frick H 《Plant physiology》1978,61(6):989-992
Cytidine deoxyriboside (Cdr), uridine deoxyriboside (Udr), and guanosine deoxyriboside (Gdr), induce quantitative bleaching of the fronds of Lemna minor (duckweed) during growth in continuous light on photoheterotrophic medium. Cdr-induced bleaching is not accompanied by a reduction in frond multiplication rate, but Udr- and Gdr-induced bleaching is. Bleaching by Cdr is fully prevented by thymidine (Tdr), cytidine (Cr), or uridine (Ur), but not by orotic acid (OA) which itself inhibits growth. Bleaching by Udr is not antagonized by Tdr, Cdr, Cr, Ur, or OA. The ability of Cdr to induce phenocopies of chlorophyll-deficient mutants in the absence of effect on growth rate is interpreted as indicating a functional compartmentation of pyrimidine metabolism between chloroplast and whole cell. On the assumption that Cdr induces bleaching by regulating the biosynthesis of deoxynucleoside triphosphates, and in analogy with the antagonism of fluorodeoxyuridine effects on growth by Tdr, Cr, or Ur, the suggestion is made that deoxycytidine is converted to thymidylate by a step other than that utilizing thymidylate synthetase. 相似文献
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Exploring the Diversity of Plant Metabolism 总被引:1,自引:0,他引:1