Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.1.1.49 (phosphoenolpyruvate carboxykinase)
 4,654 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific activities of NADP-malic enzyme, NAD-malic enzyme, phosphoenolpyruvate carboxykinase and pyruvate, orthophosphate dikinase in various cells of Vicia faba L. leaflets were determined. Expressed on dry weight, chlorophyll or protein basis, the averages for NADP- and NAD-malic enzyme specific activities were higher in guard cells than in photosynthetic parenchyma cells. Malic enzyme-specific activities were also high in epidermal cells. Phosphoenolypyruvate carboxykinase activity was not detected in Vicia leaf extracts or guard cells; the assay techniques were validated by mixed Vicia-Brachiaria leaf extraction and assays on nanogram samples of Brachiaria bundlesheath cells. It was inferred from these data that guard cell malate depletion is by decarboxylation to pyruvate in the epidermal layer, but how the various epidermal cells interact remains obscure.Pyruvate, orthophosphate dikinase activity could not be demonstrated unequivocally in Vicia leaf extracts, Vicia guard cell protoplast extracts, or in Vicia guard cells. The assay techniques were validated by mixed Vicia-Kochia leaf extraction and assays on nanogram samples of Kochia mesophyll cells. How (or if) pyruvate is phosphorylated by epidermal tissue for entry into gluconeogenesis is unknown.
 ...
PMID:High Levels of Malic Enzyme Activities in Vicia faba L. Epidermal Tissue. 1666 49

Soluble protein has been extracted from sections of wheat leaves, from base to tip, and the content of several key enzymes of photosynthetic carbon assimilation in each section has been determined by the protein blot method. In the first leaf, ribulose 1,5-bisphosphate carboxylase (RuBPC) (EC 4.1.1.39) in the basal 0 to 1 centimeter section is about 12% the level in the tip section, whereas phosphoenolpyruvate carboxylase (EC 4.1.1.31) is present in small amounts in the basal section and does not change much in the tip. Pyruvate orthophosphate dikinase (PPDK) (EC 2.7.9.1) first appears in the 4 to 6 centimeter section and increases gradually with development to 10-fold in the tip. Malic enzyme, NADP-dependent (EC 1.3.1.37) also appears in the 4 to 6 centimeter section but remains low to the tip.Fixation of (14)CO(2) by wheat leaf base sections resulted in 42% of total incorporation into malate and aspartate, indicating beta-carboxylation, whereas in the tip section these labeled compounds were only 8% of the total. Although the amount of PPDK in wheat leaves is only 1 to 3% of that in maize leaves, this C(3) PPDK may have a limited role in photosynthesis leading to formation of C(4) compounds. The possibility of a further role, similar to that in C(4) plants, but for intracellular carbon transport in wheat leaves is discussed. The presence of malic dehydrogenase, NADP-specific (EC 1.1.1.82) in wheat leaf chloroplasts was shown, a necessary though not sufficient condition for such a proposed role. Assuming each of the four enzymes associated with C(4) carbon transport were fully active in vivo during photosynthesis, PPDK would still be rate limiting, even in the leaf tip where its activity is maximal. Possible evolutionary and breeding implications are discussed.
 ...
PMID:Appearance and accumulation of c(4) carbon pathway enzymes in developing wheat leaves. 1666 22

Microbial systems are known to elaborate intricate metabolic strategies in an effort to fend the toxic impact of numerous metals. In this study, we show that the exposure of Pseudomonas fluorescens to aluminum (Al) resulted in a metabolic shift aimed at diverting oxaloacetate towards the biogenesis of an aluminophore. This metabolic alteration was characterized by uncoupling of two gluconeogenic enzymes, namely pyruvate carboxylase (PC) and phosphoenolpyruvate carboxykinase (PEPCK). While PC displayed a sharp increase in activity and expression, PEPCK was severely diminished. Malic enzyme (ME) and NAD kinase (NADK), two enzymes involved in maintaining a reductive environment, were markedly increased in the Al-stressed cells. Hence, Al-exposed Pseudomonas fluorescens evoked a metabolic response aimed at generating oxaloacetate and promoting an intracellular reductive environment.
 ...
PMID:Metabolic adaptation and oxaloacetate homeostasis in P. fluorescens exposed to aluminum toxicity. 1872 May 1


<< Previous 1 2