The Experts below are selected from a list of 198 Experts worldwide ranked by ideXlab platform
Leticia Ramirezsilva - One of the best experts on this subject based on the ideXlab platform.
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new insights on the mechanism of the k independent activity of crenarchaeota pyruvate kinases
PLOS ONE, 2015Co-Authors: Gustavo De La Vegaruiz, Lenin Dominguezramirez, Hector Riverosrosas, Carlos Guerreromendiola, Alfredo Torreslarios, Gloria Hernandezalcantara, Jose J Garciatrejo, Leticia RamirezsilvaAbstract:Eukarya pyruvate kinases have glutamate at position 117 (numbered according to the rabbit Muscle Enzyme), whereas in Bacteria have either glutamate or lysine and in Archaea have other residues. Glutamate at this position makes pyruvate kinases K+-dependent, whereas lysine confers K+-independence because the positively charged residue substitutes for the monovalent cation charge. Interestingly, pyruvate kinases from two characterized Crenarchaeota exhibit K+-independent activity, despite having serine at the equivalent position. To better understand pyruvate kinase catalytic activity in the absence of K+ or an internal positive charge, the Thermofilum pendens pyruvate kinase (valine at the equivalent position) was characterized. The Enzyme activity was K+-independent. The kinetic mechanism was random order with a rapid equilibrium, which is equal to the mechanism of the rabbit Muscle Enzyme in the presence of K+ or the mutant E117K in the absence of K+. Thus, the substrate binding order of the T. pendens Enzyme was independent despite lacking an internal positive charge. Thermal stability studies of this Enzyme showed two calorimetric transitions, one attributable to the A and C domains (Tm of 99.2°C), and the other (Tm of 105.2°C) associated with the B domain. In contrast, the rabbit Muscle Enzyme exhibits a single calorimetric transition (Tm of 65.2°C). The calorimetric and kinetic data indicate that the B domain of this hyperthermophilic Enzyme is more stable than the rest of the protein with a conformation that induces the catalytic readiness of the Enzyme. B domain interactions of pyruvate kinases that have been determined in Pyrobaculum aerophilum and modeled in T. pendens were compared with those of the rabbit Muscle Enzyme. The results show that intra- and interdomain interactions of the Crenarchaeota Enzymes may account for their higher B domain stability. Thus the structural arrangement of the T. pendens pyruvate kinase could allow charge-independent catalysis.
Leticia Ramírez-silva - One of the best experts on this subject based on the ideXlab platform.
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New insights on the mechanism of the K(+-) independent activity of crenarchaeota pyruvate kinases.
PloS one, 2015Co-Authors: Gustavo De La Vega-ruíz, Lenin Domínguez-ramírez, Héctor Riveros-rosas, Carlos Guerrero-mendiola, Alfredo Torres-larios, Gloria Hernández-alcántara, José J. García-trejo, Leticia Ramírez-silvaAbstract:Eukarya pyruvate kinases have glutamate at position 117 (numbered according to the rabbit Muscle Enzyme), whereas in Bacteria have either glutamate or lysine and in Archaea have other residues. Glutamate at this position makes pyruvate kinases K+-dependent, whereas lysine confers K+-independence because the positively charged residue substitutes for the monovalent cation charge. Interestingly, pyruvate kinases from two characterized Crenarchaeota exhibit K+-independent activity, despite having serine at the equivalent position. To better understand pyruvate kinase catalytic activity in the absence of K+ or an internal positive charge, the Thermofilum pendens pyruvate kinase (valine at the equivalent position) was characterized. The Enzyme activity was K+-independent. The kinetic mechanism was random order with a rapid equilibrium, which is equal to the mechanism of the rabbit Muscle Enzyme in the presence of K+ or the mutant E117K in the absence of K+. Thus, the substrate binding order of the T. pendens Enzyme was independent despite lacking an internal positive charge. Thermal stability studies of this Enzyme showed two calorimetric transitions, one attributable to the A and C domains (Tm of 99.2°C), and the other (Tm of 105.2°C) associated with the B domain. In contrast, the rabbit Muscle Enzyme exhibits a single calorimetric transition (Tm of 65.2°C). The calorimetric and kinetic data indicate that the B domain of this hyperthermophilic Enzyme is more stable than the rest of the protein with a conformation that induces the catalytic readiness of the Enzyme. B domain interactions of pyruvate kinases that have been determined in Pyrobaculum aerophilum and modeled in T. pendens were compared with those of the rabbit Muscle Enzyme. The results show that intra- and interdomain interactions of the Crenarchaeota Enzymes may account for their higher B domain stability. Thus the structural arrangement of the T. pendens pyruvate kinase could allow charge-independent catalysis.
Livanova Nb - One of the best experts on this subject based on the ideXlab platform.
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Structure and regulation of the activity of Muscle phosphorylase kinase
Biochemistry, 1993Co-Authors: Livanova NbAbstract:: Phosphorylase kinase is the key Enzyme in the control of glycogen metabolism in skeletal Muscles, the heart and the liver. The quaternary structure of the Enzyme, the primary structure of the Enzyme subunits as well as the kinetic properties and regulation of the skeletal Muscle Enzyme activity by covalent modification, phosphorylation and some physiological effectors (Ca2+, calmodulin, troponin C) are reviewed.
Subhankar Ray - One of the best experts on this subject based on the ideXlab platform.
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Identification of a critical lysine residue at the active site in glyceraldehyde-3-phosphate dehydrogenase of Ehrlich ascites carcinoma cell. Comparison with the rabbit Muscle Enzyme.
European journal of biochemistry, 2001Co-Authors: Swapna Ghosh, Kasturi Mukherjee, Manju Ray, Subhankar RayAbstract:The involvement of the lysine residue present at the active site of Ehrlich ascites carcinoma (EAC) cell glyceraldehyde-3-phosphate dehydrogenase (Gra3PDH) was investigated by using the lysine specific reagents trinitrobenzenesulfonic acid (TNBS) and pyridoxal phosphate (PP). Both TNBS and PP inactivated EAC cell Gra3PDH with pseudo-first-order kinetics with the rate dependent on modifier concentration. Kinetic analysis, including a Tsou plot, indicated that both TNBS and PP apparently react with one lysine residue per Enzyme molecule. Two of the substrates, d-glyceraldehyde-3-phosphate and NAD, and also NADH, the product and competitive inhibitor, almost completely protected the Enzyme from inactivation by TNBS. A comparative study of Gra3PDH of EAC cell and rabbit Muscle indicates that the nature of active site of the Enzyme is significantly different in these two cells. A double inhibition study using 5,5'-dithiobis(2-nitrobenzoic acid) and TNBS and subsequent reactivation of only the rabbit Muscle Enzyme by dithiothreitol suggested that a cysteine residue of this Enzyme possibly reacts with TNBS. These studies on the other hand, confirm that an essential lysine residue is involved in the catalytic activity of the EAC cell Enzyme. This difference in the nature of the active site of EAC cell Gra3PDH that may be related to the high glycolysis of malignant cells has been discussed.
Gustavo De La Vegaruiz - One of the best experts on this subject based on the ideXlab platform.
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new insights on the mechanism of the k independent activity of crenarchaeota pyruvate kinases
PLOS ONE, 2015Co-Authors: Gustavo De La Vegaruiz, Lenin Dominguezramirez, Hector Riverosrosas, Carlos Guerreromendiola, Alfredo Torreslarios, Gloria Hernandezalcantara, Jose J Garciatrejo, Leticia RamirezsilvaAbstract:Eukarya pyruvate kinases have glutamate at position 117 (numbered according to the rabbit Muscle Enzyme), whereas in Bacteria have either glutamate or lysine and in Archaea have other residues. Glutamate at this position makes pyruvate kinases K+-dependent, whereas lysine confers K+-independence because the positively charged residue substitutes for the monovalent cation charge. Interestingly, pyruvate kinases from two characterized Crenarchaeota exhibit K+-independent activity, despite having serine at the equivalent position. To better understand pyruvate kinase catalytic activity in the absence of K+ or an internal positive charge, the Thermofilum pendens pyruvate kinase (valine at the equivalent position) was characterized. The Enzyme activity was K+-independent. The kinetic mechanism was random order with a rapid equilibrium, which is equal to the mechanism of the rabbit Muscle Enzyme in the presence of K+ or the mutant E117K in the absence of K+. Thus, the substrate binding order of the T. pendens Enzyme was independent despite lacking an internal positive charge. Thermal stability studies of this Enzyme showed two calorimetric transitions, one attributable to the A and C domains (Tm of 99.2°C), and the other (Tm of 105.2°C) associated with the B domain. In contrast, the rabbit Muscle Enzyme exhibits a single calorimetric transition (Tm of 65.2°C). The calorimetric and kinetic data indicate that the B domain of this hyperthermophilic Enzyme is more stable than the rest of the protein with a conformation that induces the catalytic readiness of the Enzyme. B domain interactions of pyruvate kinases that have been determined in Pyrobaculum aerophilum and modeled in T. pendens were compared with those of the rabbit Muscle Enzyme. The results show that intra- and interdomain interactions of the Crenarchaeota Enzymes may account for their higher B domain stability. Thus the structural arrangement of the T. pendens pyruvate kinase could allow charge-independent catalysis.
