RESUMO
(-)-Epicatechin-3,5-O-digallate (ECDG) from Orostachys japonicus A. Berger was examined for inhibitory activity on α-glucosidase. The results showed that the IC50 value was achieved with nanomolar concentrations. Through the enzyme kinetic analysis, ECDG was shown to act as a competitive inhibitor of α-glucosidase by binding to the receptor active site. Fluorescence-quenching measurements showed that ECDG and the enzyme may have a one-to-one reaction with low quenching (Ksv) and binding constants. A molecular docking study was performed to evaluate the receptor-ligand complex. Asn236 was found to be particularly important for hydrogen bond formation during the molecular dynamics simulation.
Assuntos
Catequina/análogos & derivados , Crassulaceae/enzimologia , Inibidores de Glicosídeo Hidrolases/química , alfa-Glucosidases/química , Sítios de Ligação , Catequina/química , Catequina/farmacologia , Simulação por Computador , Inibidores de Glicosídeo Hidrolases/farmacologia , Ligação de Hidrogênio , Cinética , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Conformação ProteicaRESUMO
In plants with crassulacean acid metabolism (CAM), dark CO2 uptake is mediated by phosphoenolpyruvate carboxylase (PEPC), an enzyme that can be regulated at transcriptional and posttranslational levels. Reversible phosphorylation of PEPC is catalyzed by a dedicated PEPC kinase, which in turn is regulated at the transcriptional level over the 24-h cycle in CAM plants. PEPC kinase controls the day/night regulation of PEPC during the CAM cycle, thus facilitating plasticity for optimizing CO2 uptake under different environmental conditions. To understand the importance of PEPC kinase in relation to its target PEPC in terms of CAM performance, the expression of the genes encoding the two enzymes was investigated in four species of Clusia that have photosynthetic patterns ranging from C3 photosynthesis to constitutive CAM. By linking changes in the expression of PEPC and PEPC kinase to day/night patterns of leaf gas exchange, organic acid, and soluble sugar contents under different environmental conditions, the genetic and metabolic limitations to CAM plasticity were assessed. The results indicate that PEPC expression is a major factor underpinning the genotypic capacity for CAM and that PEPC kinase expression does not appear to limit CAM. The day/night regulation of Ppck transcript abundance was found to be a consequence of CAM and the day/night cycling of associated metabolites, rather than the primary controlling factor for the temporal separation of carboxylation processes.
Assuntos
Clusia/genética , Fosfoenolpiruvato Carboxilase/genética , Proteínas Serina-Treonina Quinases/genética , Sequência de Aminoácidos , Clusia/enzimologia , Crassulaceae/enzimologia , Crassulaceae/genética , Crassulaceae/metabolismo , DNA Complementar/química , DNA Complementar/genética , Desastres , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação Enzimológica da Expressão Gênica/efeitos da radiação , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Genótipo , Luz , Dados de Sequência Molecular , Fenótipo , Fosfoenolpiruvato Carboxilase/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/classificação , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Poliubiquitina/genética , Poliubiquitina/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Água/farmacologiaRESUMO
Crassulacean acid metabolism (CAM) plants exhibit persistent circadian rhythms of CO(2) metabolism. These rhythms are driven by changes in the flux through phosphoenolpyruvate carboxylase, which is regulated by reversible phosphorylation in response to a circadian oscillator. This article reviews progress in our understanding of the circadian expression of phosphoenolpyruvate carboxylase kinase.
Assuntos
Ritmo Circadiano/fisiologia , Crassulaceae/enzimologia , Fosfoenolpiruvato Carboxilase/metabolismo , Relógios Biológicos , Clonagem Molecular , Crassulaceae/genética , Regulação Enzimológica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Fosfoenolpiruvato Carboxilase/genética , FosforilaçãoRESUMO
V-ATPases pump protons into the interior of various subcellular compartments at the expense of ATP. Previous studies have shown that these pumps comprise a membrane-integrated, proton-translocating (V(0)), and a soluble catalytic (V(1)) subcomplex connected to one another by a thin stalk region. We present two three-dimensional maps derived from electron microscopic images of the complete V-ATPase complex from the plant Kalanchoë daigremontiana at a resolution of 2.2 nm. In the presence of a non-hydrolyzable ATP analogue, the details of the stalk region between V(0) and V(1) were revealed for the first time in their three-dimensional organization. A central stalk was surrounded by three peripheral stalks of different sizes and shapes. In the absence of the ATP analogue, the tilt of V(0) changed with respect to V(1), and the stalk region was less clearly defined, perhaps due to increased flexibility and partial detachment of some of the peripheral stalks. These structural changes corresponded to decreased stability of the complex and might be the initial step in a controlled disassembly.
