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Kinetic and Chemical Mechanism of Pyrophosphate-Dependent PhosphofructokinaseCho, Yong Kweon 12 1900 (has links)
Data obtained from isotope exchange at equilibrium, exchange of inorganic phosphate against forward reaction flux, and positional isotope exchange of 18O from the (βγ-bridge position of pyrophosphate to a (β-nonbridge position all indicate that the pyrophosphate-dependent phosphofructokinase from Propionibacterium freudenreichii has a rapid equilibrium random kinetic mechanism. All exchange reactions are strongly inhibited at high concentrations of the fructose 6-phosphate/Pi and MgPPi/Pi substrate-product pairs and weakly inhibited at high concentrations of the MgPPi/fructose 1,6-bisphosphate pair suggesting three dead-end complexes, E:F6P:Pi, E:MgPPi:Pi, and E:FBP:MgPPi. Neither back-exchange by [32p] nor positional isotope exchange of 18O-bridge-labeled pyrophosphate was observed under any conditions, suggesting that either the chemical interconversion step or a step prior to it limits the overall rate of the reaction. Reduction of the pyridoxal 5'-phosphate-inactivated enzyme with NaB[3H]4 indicates that about 7 lysines are modified in free enzyme and fructose 1,6-bisphosphate protects 2 of these from modification. The pH dependence of the enzyme-reactant dissociation constants suggests that the phosphates of fructose 6-phosphate, fructose 1,6-bisphosphate, inorganic phosphate, and Mg-pyrophosphate must be completely ionized and that lysines are present in the vicinity of the 1- and 6-phosphates of the sugar phosphate and bisphosphates probably directly coordinated to these phosphates. The pH dependence of kinetic parameters suggests that the enzyme catalyzes its reaction via general acid-base catalysis with the use of a proton shuttle. The base is required unprotonated in both reaction directions. In the direction of fructose 6-phosphate phosphorylation the base accepts a proton from the hydroxyl at C-l of F6P and then donates it to protonate the leaving phosphate. The maximum velocity of the reaction is pH independent in both reaction directions while V/K profiles exhibit pKs for binding groups (including enzyme and reactant functional groups) as well as pKs for enzyme catalytic groups. These data suggest that reactants bind only when correctly protonated and only to the correctly protonated form of the enzyme.
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The catalytic mechanism of Bacillus stearothermophilus pyruvate kinaseScotney, Pierre David January 1999 (has links)
No description available.
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Enzyme activity in cultures of the marine macroalgae Laminaria saccharina and Ochtodes secundirameaTucker, Mary 19 March 1999 (has links)
Graduation date: 1999
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Design, synthesis, and evaluation of novel irreversible inhibitors for caspasesEkici, Özlem Doğan, January 2003 (has links) (PDF)
Thesis (Ph. D.)--School of Chemistry and Biochemistry, Georgia Institute of Technology, 2004. Directed by James C. Powers. / Vita. Includes bibliographical references (leaves 132-151).
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Acetylcholinesterase in the sea urchin Lytechinus variegatus characterization and developmental expression in larvae /Jennings, Natalie A. January 2007 (has links) (PDF)
Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Description based on contents viewed Oct. 2, 2008; title from PDF t.p. Includes bibliographical references (p. 34-42).
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Multidimensional methods applications in drug-enzyme intrinsic clearance determination and comprehensive two-dimensional liquid chromatography peak volume determination /Thekkudan, Dennis Francis, January 1900 (has links)
Thesis (Ph.D.)--Virginia Commonwealth University, 2009. / Prepared for: Dept. of Chemistry. Title from title-page of electronic thesis. Bibliography: leaves 144-153.
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Structural and kinetic studies of two enzymes catalyzing phospholipase A2 activityEpstein, Todd Matthew. January 2006 (has links)
Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Brian J. Bahnson, Dept. of Chemistry and Biochemistry. Includes bibliographical references.
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The mechanism of papain and ficin-catalysed hydrolysesLake, A. W. January 1967 (has links)
No description available.
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Synthesis and interaction of secondary N-nitrosamines with acetylcholinesteraseMmutle, Tsietso Bernard January 1991 (has links)
Secondary N-nitrosamines: diphenylnitrosamine (DPhNA), dimethylnitrosamine (DMNA), diethylnitrosamine (DENA), dipropylnitrosamine (DPNA), dibutylnitrosamine (DBNA), diethanolnitrosamine (DEtNA), methylnitrosoglycine (MNGly), nitrosopyrrolidine (NPyr), nitrosomorpholine (NMor) and nitrosopiperidine (NPip) were synthesised and their interaction with acetylcholinesterase (AChE) was investigated. Analyses of kinetic results show that DMNA (Ki=34.78 μM); DENA (Ki=54.24 μM); DPNA(Ki=60.36 μM); DBNA(Ki=95.54 μM); DEtNA(Ki=43.68 μM)MNGly (Ki=30.18 μM); NPip (Ki=123 μM); NPyr (Ki=66.07 μM), NMor (Ki=73.93 μM) and DPhNA (Ki=20.32 μM) are competitive and reversible inhibitors of acetylcholinesterase, with respect to the substrate, acetylthiocholine chloride, ATChCl. With time they act as irreversible covalent inhibitors with dipropy1nitrosamine producing 72% inactivation after 60 minutes. Scatchard analyses of f1uorometric titrations, (Kd=0.75mM-4.09mM); gel chromatography (Kd=O. 80mM-4. 60mM) and equilibrium dia1ysis (Kd=O. 71mM- 4.21mM) for MNG1y, DMNA, DEtNA, DENA, DPNA, NPyr, DSNA, NMor and NPip show that these compounds have weaker affinity for the enzyme, as compared to the much tightly binding aromatic DPhNA, Kd values (0.65mM, 0.68mM and 0.68mM) for fluorometric experiments, gel chromatography and equilibrium dialysis respectively. In all cases, the number of binding sites of acetylcholinesterase averaged to four.
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Synthesis and MAO activity of a series of benzimidazolyl and indazolyl prodrugsDowney, Aaron 20 November 2006 (has links)
Parkinson's disease (PD) is a chronic, progressive disorder of the central nervous system that affects approximately 1.5 million Americans. One of the principal pathological features of PD is dopamine deficiency in the substantia nigra of the brain. A key enzyme that has been associated with the neurodegeneration seen in PD is monoamine oxidase-B (MAO-B). Several inhibitors of this enzyme have resulted in neuroprotection in the mouse model of PD. One such compound is 7-nitroindazole (1).
This thesis describes the synthesis and MAO activity of several indazolyl and benzimidazolyl prodrugs that are designed to release an enzyme inhibitor in the affected brain area. These studies have provided information regarding the nucleophilic aromatic substitutions of the ambident nucleophiles under consideration. We have also discovered a compound that releases the enzyme inhibitor upon bioactivation by MAO. These results as well as a MPTP mouse study with the aforementioned compound are detailed within. / Master of Science
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