General base-general acid catalysis by terpenoid cyclases
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چکیده
منابع مشابه
Concerted General Base and Bifunctional General Acid Catalysis of the Aminolysis of Phenyl Acetate by Pyrazole'
The reaction of phenyl acetate with pyrazole is catalyzed by general bases and by bifunctional general acids. The Br~lnsted plot for general base catalysis shows downward curvature. It is consistent with either a Hammond effect on proton transfer, as described by a positive coefficient p x = a/3/-apKAH, or separate lines with p = 0.65 for cacodylate and substituted acetate monoanions and /3 = 0...
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Bovine pancreatic ribonuclease A (RNase A; EC 3.1.27.5) has been one of the most studied of all enzymes.’ RNase A efficiently catalyzes the cleavage of RNA.2 Early X-ray diffraction analyses revealed that the active site of RNase A contains two histidine residues, histidine 12 (H12) and histidine 119 (H1 19).3 The results of chemical modification4 and pHrate’ studies are consistent with an enzy...
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Several small ribozymes carry out self-cleavage at a specific phosphodiester bond to yield 2',3'-cyclic phosphate and 5'-hydroxyl termini. Prior mechanistic and structural studies on the HDV ribozymes led to the proposal that the pK(a) of C75 is shifted toward neutrality, making it an effective general acid. Recent mechanistic studies on the hairpin ribozyme have led to models in which protonat...
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Inferences about the catalytic mechanism of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) are frequently made on the basis of a presumed analogy with chymotrypsin, EC 3.4.21.1. Although both enzymes are serine hydrolases, several differences in the steady-state kinetic properties of the two have been observed. In this report particular attention is focused on the second-order react...
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Acid-base interactions have found numerous applications in research dealing with adsorption of molecules of liquids on the surfaces of solids. The main focus of this research is to estimate the thermodynamic work of adhesion, determine mechanism of interactions, analyze the morphology of interfaces and various surface coatings, develop surface modifiers, study the aggregation of macromolecular ...
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ژورنال
عنوان ژورنال: The Journal of Antibiotics
سال: 2016
ISSN: 0021-8820,1881-1469
DOI: 10.1038/ja.2016.39