Enzyme Catalysis
Mostrando 25-36 de 558 artigos, teses e dissertações.
-
25. Network of coupled promoting motions in enzyme catalysis
A network of coupled promoting motions in the enzyme dihydrofolate reductase is identified and characterized. The present identification is based on genomic analysis for sequence conservation, kinetic measurements of multiple mutations, and mixed quantum/classical molecular dynamics simulations of hydride transfer. The motions in this network span time scale
The National Academy of Sciences.
-
26. A conserved catalytic residue in the ubiquitin-conjugating enzyme family
Ubiquitin (Ub) regulates diverse functions in eukaryotes through its attachment to other proteins. The defining step in this protein modification pathway is the attack of a substrate lysine residue on Ub bound through its C-terminus to the active site cysteine residue of a Ub-conjugating enzyme (E2) or certain Ub ligases (E3s). So far, these E2 and E3 cystei
Oxford University Press.
-
27. Effects of transition metals on nitric oxide synthase catalysis
The biosynthesis of nitric oxide (NO) by the enzyme NO synthase (NOS) proceeds by the hydroxylation of l-arginine to form NG-hydroxy-l-arginine followed by the conversion of NG-hydroxy-l-arginine to l-citrulline and NO. The previously identified requirements of this relatively complicated reaction include several protein-bound cofactors: cytochrome P450-type
The National Academy of Sciences.
-
28. Vitamin B6-Responsive Histidine Deficiency in Mutants of Salmonella typhimurium
A mutant of Salmonella typhimurium LT-2 that requires either vitamin B6 or histidine for growth was found to synthesize vitamin B5 in amounts comparable to the parent strain, but to be deficient in imidazoleacetol phosphate transaminase (L-histidinolphosphate: 2-oxoglutarate aminotransferase, EC 2.6.1.9), an enzyme required for histidine biosynthesis. The mu
-
29. The mechanism of catalysis of the chorismate to prephenate reaction by the Escherichia coli mutase enzyme
Molecular dynamics studies of the Escherichia coli chorismate mutase (EcCM), containing at the active site chorismate and in turn the transition state (TS), have been performed. The simulations show that TS is not bound any tighter than chorismate. Comparison of average polar interactions show they are virtually identical for interactions of EcCM with choris
The National Academy of Sciences.
-
30. Transition state structure of arginine kinase: Implications for catalysis of bimolecular reactions
Arginine kinase belongs to the family of enzymes, including creatine kinase, that catalyze the buffering of ATP in cells with fluctuating energy requirements and that has been a paradigm for classical enzymological studies. The 1.86-Å resolution structure of its transition-state analog complex, reported here, reveals its active site and offers direct evide
The National Academy of Sciences.
-
31. Escherichia coli DNA Adenine Methyltransferase: THE STRUCTURAL BASIS OF PROCESSIVE CATALYSIS AND INDIRECT READ-OUT
We have investigated the structural basis of processive GATC methylation by the Escherichia coli DNA adenine methyltransferase, which is critical in chromosome replication and mismatch repair. We determined the contribution of the orthologically conserved phosphate interactions involving residues Arg95, Asn126, Asn132, Arg116, and Lys139, which directly cont
American Society for Biochemistry and Molecular Biology.
-
32. Identification of Essential Glutamates in the Acetate Kinase from Methanosarcina thermophila
Acetate kinase catalyzes the reversible phosphorylation of acetate (CH3COO− + ATP⇄CH3CO2PO32− + ADP). A mechanism which involves a covalent phosphoryl-enzyme intermediate has been proposed, and chemical modification studies of the enzyme from Escherichia coli indicate an unspecified glutamate residue is phosphorylated (J. A. Todhunter and D. L. Purich,
American Society for Microbiology.
-
33. Chemical complementation: A reaction-independent genetic assay for enzyme catalysis
A high-throughput assay for enzyme activity has been developed that is reaction independent. In this assay, a small-molecule yeast three-hybrid system is used to link enzyme catalysis to transcription of a reporter gene in vivo. Here we demonstrate the feasibility of this approach by using a well-studied enzyme-catalyzed reaction, cephalosporin hydrolysis by
National Academy of Sciences.
-
34. Characterization of an altered DNA catalysis of a camptothecin-resistant eukaryotic topoisomerase I.
We investigated topoisomerase I activity at a specific camptothecin-enhanced cleavage site by use of a partly double-stranded DNA substrate. The cleavage site belongs to a group of DNA topoisomerase I sites which is only efficiently cleaved by wild-type topoisomerase I (topo I-wt) in the presence of camptothecin. With a mutated camptothecin-resistant form of
-
35. Rate Acceleration by Stereopopulation Control: Models for Enzyme Action
As a result of alkyl substitution in both aromatic ring and side chain, the rate constant for acid-catalyzed lactonization of hydrocoumaric acid is increased by factors as high as 1011 and, in comparison with the bimolecular esterification of phenol and acetic acid, by almost 1016. In the most favorable case studied, the half-life of the phenolic acid (imida
-
36. Purification and Characterization of l-Methionine γ-Lyase from Brevibacterium linens BL2†
l-Methionine γ-lyase (EC 4.4.1.11) was purified to homogeneity from Brevibacterium linens BL2, a coryneform bacterium which has been used successfully as an adjunct bacterium to improve the flavor of Cheddar cheese. The enzyme catalyzes the α,γ elimination of methionine to produce methanethiol, α-ketobutyrate, and ammonia. It is a pyridoxal phosphate-dep
American Society for Microbiology.