Elucidation of a [4Fe-4S] cluster degradation pathway: rapid kinetic studies of the degradation of Chromatium vinosum HiPIP

2001 ◽  
Vol 6 (3) ◽  
pp. 266-274 ◽  
Author(s):  
Matthew W. Foster ◽  
Shumin Bian ◽  
Kristene K. Surerus ◽  
J.A. Cowan
Keyword(s):  
Kinetic Studies ◽  
Degradation Pathway ◽  
Chromatium Vinosum

Free-radical-induced oxidative and reductive degradation of N,N′-diethyl-m-toluamide (DEET): Kinetic studies and degradation pathway

2009 ◽  
Vol 43 (3) ◽  
pp. 635-642 ◽  
Author(s):  
Weihua Song ◽  
William J. Cooper ◽  
Barrie M. Peake ◽  
Stephen P. Mezyk ◽  
Michael G. Nickelsen ◽  
...  
Keyword(s):  
Free Radical ◽  
Kinetic Studies ◽  
Degradation Pathway ◽  
Reductive Degradation

Photocatalytic Decomposition of Metoprolol and Its Intermediate Organic Reaction Products: Kinetics and Degradation Pathway

2016 ◽  
Vol 14 (3) ◽  
pp. 809-820 ◽  
Author(s):  
Alfonso Pinedo ◽  
Mariana López ◽  
Elisa Leyva ◽  
Brenda Zermeño ◽  
Benito Serrano ◽  
...  
Keyword(s):  
Uv Light ◽  
Reaction Pathway ◽  
Kinetic Studies ◽  
Initial Reaction Rate ◽  
Degradation Pathway ◽  
Photocatalytic Decomposition ◽  
Initial Reaction ◽  
Low Molecular Weight ◽  
Reaction Products ◽  
Constant Flow Rate

Abstract High purity metoprolol prepared by neutralization of an aqueous solution of metoprolol tartrate is efficiently mineralized to CO2 and water by photocatalysis with TiO2, UV light and a constant flow rate of oxygen. Since the tartrate anions were eliminated, all the HO• generated by photocatalysis reacted efficiently with the aromatic part of the medication. The reaction pathway includes two routes of degradation. The first one includes the transformation of metoprolol to hydroquinone via formation of 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde. Metoprolol is also degraded directly to hydroquinone. Then, this aromatic compound is oxidized to 1,2,4-benzenetriol, which is rapidly oxidized to low molecular weight organic acids before being completely mineralized to CO2 and water. Kinetic studies indicated that the initial reaction rate of the degradation of metoprolol, 4-(2-methoxyethyl)phenol, 2-(4-hydroxyphenyl)ethanol and 4-hydroxybenzaldehyde is described by the LH-HW model.

scholarly journals Identification of Novel Vesicles in the Cytosol to Vacuole Protein Degradation Pathway

1997 ◽  
Vol 136 (4) ◽  
pp. 803-810 ◽  
Author(s):  
Pei-Hsin Huang ◽  
Hui-Ling Chiang
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Degradation ◽  
High Speed ◽  
Kinetic Studies ◽  
Degradation Pathway ◽  
Proteinase K ◽  
Wild Type ◽  
Fractionation Analysis ◽  
Gluconeogenic Enzyme ◽  
Copii Vesicles

The key gluconeogenic enzyme, fructose1,6-bisphosphatase (FBPase), is induced when Saccharomyces cerevisiae are starved of glucose. FBPase is targeted from the cytosol to the yeast vacuole for degradation when glucose-starved cells are replenished with fresh glucose. Several vid mutants defective in the glucose-induced degradation of FBPase in the vacuole have been isolated. In some vid mutants, FBPase is found in punctate structures in the cytoplasm. When extracts from these cells are fractionated, a substantial amount of FBPase is sedimentable in the high speed pellet, suggesting that FBPase is associated with intracellular structures in these vid mutants. In this paper we investigated whether FBPase association with intracellular structures also existed in wild-type cells. We report the purification of novel FBPase-associated vesicles from wild-type cells to near homogeneity. Kinetic studies indicate that FBPase association with these vesicles is stimulated by glucose and occurs only transiently, suggesting that these vesicles are intermediate in the FBPase degradation pathway. Fractionation analysis demonstrates that these vesicles are distinct from known organelles such as the vacuole, ER, Golgi, mitochondria, peroxisomes, endosomes, COPI, or COPII vesicles. Under EM, these vesicles are 30–40 nm in diam. Proteinase K experiments indicate that the majority of FBPase is sequestered inside the vesicles. We propose that FBPase is imported into these vesicles before entering the vacuole.

scholarly journals Dissociation from BiP and Retrotranslocation of Unassembled Immunoglobulin Light Chains Are Tightly Coupled to Proteasome Activity

2000 ◽  
Vol 11 (1) ◽  
pp. 217-226 ◽  
Author(s):  
Josep Chillarón ◽  
Ingrid G. Haas
Keyword(s):  
Half Life ◽  
Physical Stability ◽  
Kinetic Studies ◽  
Subcellular Fractionation ◽  
Degradation Pathway ◽  
Proteasome Activity ◽  
Light Chains ◽  
Immunoglobulin Light Chains ◽  
Tightly Coupled

Unassembled immunoglobulin light chains expressed by the mouse plasmacytoma cell line NS1 (κNS1) are degraded in vivo with a half-life of 50–60 min in a way that closely resembles endoplasmic reticulum (ER)-associated degradation ( Knittler et al., 1995 ). Here we show that the peptide aldehydes MG132 and PS1 and the specific proteasome inhibitor lactacystin effectively increased the half-life of κNS1, arguing for a proteasome-mediated degradation pathway. Subcellular fractionation and protease protection assays have indicated an ER localization of κNS1 upon proteasome inhibition. This was independently confirmed by the analysis of the folding state of κNS1and size fractionation experiments showing that the immunoglobulin light chain remained bound to the ER chaperone BiP when the activity of the proteasome was blocked. Moreover, kinetic studies performed in lactacystin-treated cells revealed a time-dependent increase in the physical stability of the BiP–κNS1complex, suggesting that additional proteins are present in the older complex. Together, our data support a model for ER-associated degradation in which both the release of a soluble nonglycosylated protein from BiP and its retrotranslocation out of the ER are tightly coupled with proteasome activity.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

2-methylpentane catalytic reactions on Pt(3%wt)-HNaβ-zeolite. Kinetic studies

1998 ◽  
Vol 95 (3) ◽  
pp. 536-560 ◽  
Author(s):  
S. Siffert ◽  
F. Garin
Keyword(s):  
Kinetic Studies ◽  
Catalytic Reactions
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