In Vitro Phosphorylation of Maize Leaf Phosphoenolpyruvate Carboxylase

Budde, Raymond J.A.; Chollet, Raymond

doi:10.1007/978-94-017-0516-5_107

Cited by 8 publications

(12 citation statements)

References 14 publications

(21 reference statements)

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“…It should be pointed out here that PEP plus thiol have been reported to reactivate in vitro the PEPCase inactivated upon dilution in assay media at low PEP The mechanism of a PEP-induced activation is not self-evident but could be related to the phosphorylation of PEPCase observed recently (Budde andChollet 1986, Nimmo et al 1987) or to the PEP-dependent stabilization of the tetrameric form of the enzyme documented by Walker et al (1986).…”

Section: Discussionmentioning

confidence: 99%

Effects of temperature and photosynthetic inhibitors on light activation of C4-phosphoenolpyruvate carboxylase

1988

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Phosphoenolpyruvate carboxylase from leaves of the C4 plant Setaria verticillata (L.) Beauv. is activated by light; day levels of activity are reached after 30 minutes of illumination. Photoactivation is prevented by inhibitors of photosynthetic electron flow or of photophosphorylation and by D,L-glyceraldehyde, which inhibits the reductive pentose phosphate pathway.Although the extractable activity in the dark is not affected by temperature the photoactivation is prevented when both illumination and extraction are done under low temperature (5 C). High temperature (30 C) during either illumination or extraction is needed for activation. Once the enzyme is photoactivated at 30 C, a transfer of the leaves to 5 C does not abolish the extra activity.The results suggest that both unimpaired electron flow and photophosphorylation are prerequisites for the activation of phosphoenolpyruvate carboxylase. Low temperature apparently suppresses either the transport to the cytoplasm of a photosynthetic intermediate or the activating reaction itself. The inclusion of phosphoenolpyruvate in the extraction medium increases the night activity.On the basis of the available information, it is suggested that phosphoenolpyruvate could be the activator in vivo. In that case, the activation of phosphoenolpyruvate carboxylase would depend on internal CO2 level and prior photoactivation of both pyruvate, orthophosphate, dikinase and NADP malate dehydrogenase.

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Section: Discussionmentioning

confidence: 99%

Effects of temperature and photosynthetic inhibitors on light activation of C4-phosphoenolpyruvate carboxylase

1988

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“…In plants, most studies have focused on the role of PEPC in C4 and CAM (crassulacean acid metabolism) species where the enzyme provides an effective mechanism of concentrating CO2 within leaves [22,30,43]. Numerous studies have documented physical and biochemical properties of PEPC in C4 and CAM species [1,2,17,18,21,29,43] and more recently cDNAs and genomic clones which encode the enzyme in these species have been isolated [4,6,12,15,16,19,33]. The enzyme is a tetramer comprised of subunits of 100 to 110 kDa and several isoforms of PEPC have been detected in both C4 and CAM species [4,6,12,16,19].…”

Section: Introductionmentioning

confidence: 99%

“…Post-translational regulation of PEPC is achieved through phosphorylation of the protein [ 1,2,17,21], oligomerization as affected by phosphoenolpyruvate, malate and glucose-6-phosphate [29,43,44] and protein turnover [18]. By comparison, much less is known about the C3 and nonautotrophic (root) forms of PEPC.…”

Section: Introductionmentioning

confidence: 99%

Alfalfa root nodule phosphoenolpyruvate carboxylase: characterization of the cDNA and expression in effective and plant-controlled ineffective nodules

et al. 1992

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Phosphoenolpyruvate carboxylase (PEPC) plays a key role in N2 fixation and ammonia assimilation in legume root nodules. The enzyme can comprise up to 2% of the soluble protein in root nodules. We report here the isolation and characterization of a cDNA encoding the nodule-enhanced form of PEPC. Initially, a 2945 bp partial-length cDNA was selected by screening an effective alfalfa nodule cDNA library with antibodies prepared against root nodule PEPC. The nucleotide sequence encoding the N-terminal region of the protein was obtained by primer-extension cDNA synthesis and PCR amplification. The complete amino acid sequence of alfalfa PEPC was deduced from these cDNA sequences and shown to bear striking similarity to other plant PEPCs. Southern blots of alfalfa genomic DNA indicate that nodule PEPC is a member of a small gene family. During the development of effective root nodules, nodule PEPC activity increases to a level that is 10- to 15-fold greater than that in root and leaf tissue. This increase appears to be the result of increases in amount of enzyme protein and PEPC mRNA. Ineffective nodules have substantially less PEPC mRNA, enzyme protein and activity than do effective nodules. Maximum expression of root nodule PEPC appears to be related to two signals. The first signal is associated with nodule initiation while the second signal is associated with nodule effectiveness. Regulation of root nodule PEPC activity may also involve post-translational processes affecting enzyme activity and/or degradation.

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“…Even in that case, however, it is impQative to start the reaction with the enzyme in order to preserve its functional integrity against dilution in the absence of substrate. This precaution is often overlooked (Siborova and Leblova 1985;Budde and Chollet 1986), though its necessity was obvious from the results of previous work (Gavalas et al 1982). In fact, the common practice of starting the reaction with the substrate may account for some contradictory data found in the literature.…”

Section: Discussionmentioning

confidence: 99%

Organic Cosolutes Increase the Catalytic Efficiency of Phosphoenolpyruvate Carboxylase, From Cynodon Dactylon (L.) Pers., Apparently Through Self-Association of the Enzymic Protein

Stamatakis¹,

Gavalas²,

Manetas³

1988

Functional Plant Biol.

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Several organic cosolutes (glycerol, sorbitol, betaine, proline, polyethylene glycol, polyvinylpyrrolidone) increase, to a large extent and in a concentration-dependent manner, the apparent affinity of phosphoenolpyruvate carboxylase for phosphoenolpyruvate, whereas the maximum activity remains unaffected. In absence of cosolutes, a similar response is obtained as the concentration of the enzymic protein in the assay medium is increased. The effect of the organic additives does not depend on the osmotic potential or the viscosity of the medium and it could be best interpreted with the exclusion volume theory. It is inferred that the inclusion of an appropriate cosolute in the assay medium promotes the self-association of the enzymic protein and, therefore, mimics the intracellular situation, where the enzyme is much concentrated. In light of these results, it is suggested that the physiological relevance of past data concerning the non-saturating activity and the regulation of the enzyme in vivo should be reevaluated.

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In Vitro Phosphorylation of Maize Leaf Phosphoenolpyruvate Carboxylase

Cited by 8 publications

References 14 publications

Effects of temperature and photosynthetic inhibitors on light activation of C4-phosphoenolpyruvate carboxylase

Effects of temperature and photosynthetic inhibitors on light activation of C4-phosphoenolpyruvate carboxylase

Alfalfa root nodule phosphoenolpyruvate carboxylase: characterization of the cDNA and expression in effective and plant-controlled ineffective nodules

Organic Cosolutes Increase the Catalytic Efficiency of Phosphoenolpyruvate Carboxylase, From Cynodon Dactylon (L.) Pers., Apparently Through Self-Association of the Enzymic Protein

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