Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:2.4.1.14 (
SPS
)
813
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Light dependent modulation of
sucrose-phosphate synthase
activity (
SPS
;
EC 2.4.1.14
) was studied in a tree species, namely Prosopis juliflora. In this paper we demonstrate that cycloheximide, an inhibitor of
cytoplasmic protein
synthesis, when fed to detached leaves of P. juliflora through transpiration stream in the dark or in light completely prevents in vivo light activation of Vlim and Vmax activities of
SPS
. In case of spinach, however, cycloheximide feeding affects only Vlim activity while Vmax activity remained unchanged. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplast has no effect on the light activation of
SPS
in Prosopis. The treatment with cycloheximide showed slight reduction in the rate of O2 evolution indicating that cycloheximide had very little effect on overall photosynthesis. These results indicate that short term protein turnover of the
SPS
protein and some other essential component(s) (e.g., a putative protein that modifies
SPS
activity) is one of the primary steps in a complex and unique regulatory cascade effecting the reversible light activation of
SPS
.
...
PMID:Sucrose-phosphate synthase in tree species: light/dark regulation involves a component of protein turnover in Prosopis juliflora (SW DC). 935 Mar 50
Maize leaf phosphoenolpyruvate carboxylase [PEPC; orthophosphate:oxaloacetate carboxy-lyase (phosphorylating), EC 4.1.1.31] protein-serine kinase (PEPC-PK) phosphorylates serine-15 of its target enzyme, thus leading to an increase in catalytic activity and a concomitant decrease in malate sensitivity of this cytoplasmic C4 photosynthesis enzyme in the light. We have recently demonstrated that the PEPC-PK activity in maize leaves is slowly, but strikingly, increased in the light and decreased in darkness. In this report, we provide evidence that cycloheximide, an inhibitor of
cytoplasmic protein
synthesis, when fed to detached leaves of C4 monocots (maize, sorghum) and dicots (Portulaca oleracea) in the dark or light, completely prevents the in vivo light activation of PEPC-PK activity regardless of whether the protein kinase activity is assessed in vivo or in vitro. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplasts, has no effect on the light activation of maize PEPC-PK. Similarly, treatment with cycloheximide did not influence the light activation of other photosynthesis-related enzymes in maize, including cytoplasmic
sucrose-phosphate synthase
and chloroplast stromal NADPH-malate dehydrogenase and pyruvate, Pi dikinase. These and related results, in which detached maize leaves were treated simultaneously with cycloheximide and microcystin-LR, a potent in vivo and in vitro inhibitor of the PEPC type 2A protein phosphatase, indicate that short-term protein turnover of the PEPC-PK itself or some other essential component(s) (e.g., a putative protein that modifies this kinase activity) is one of the primary levels in the complex and unique regulatory cascade effecting the reversible light activation/seryl phosphorylation of PEPC in the mesophyll cytoplasm of C4 plants.
...
PMID:Protein turnover as a component in the light/dark regulation of phosphoenolpyruvate carboxylase protein-serine kinase activity in C4 plants. 1160 71
