Search results for "hydrolysis"
showing 10 items of 632 documents
Molecular Mechanism of ATP Hydrolysis in an ABC Transporter
2018
Hydrolysis of nucleoside triphosphate (NTP) plays a key role for the function of many biomolecular systems. However, the chemistry of the catalytic reaction in terms of an atomic-level understanding of the structural, dynamic, and free energy changes associated with it often remains unknown. Here, we report the molecular mechanism of adenosine triphosphate (ATP) hydrolysis in the ATP-binding cassette (ABC) transporter BtuCD-F. Free energy profiles obtained from hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations show that the hydrolysis reaction proceeds in a stepwise manner. First, nucleophilic attack of an activated lytic water molecule at the ATP γ-…
Electrochemical modifications of proteins: disulfide bonds reduction
2002
International audience; Electrochemical reduction of lysozyme disulfide bonds was achieved at pH between 10 and 11.Below pH 10, no disulfide bond cleavage was observed. At pH higher than 12, the cleavage of disulfide bonds is essentially due to hydrolysis. The addition of denaturant considerably enhanced the performance of the electrochemical device.
Metabolic detoxification: implications for thresholds.
2000
The fact that chemical carcinogenesis involves single, isolated, essentially irreversible molecular events as discrete steps, several of which must occur in a row to finally culminate in the development of a malignancy, rather suggests that an absolute threshold for chemical carcinogens may not exist. However, practical thresholds may exist due to saturable pathways involved in the metabolic processing, especially in the metabolic inactivation, of such compounds. An important example for such a pathway is the enzymatic hydrolysis of epoxides via epoxide hydrolases, a group of enzymes for which the catalytic mechanism has recently been established. These enzymes convert their substrates via…
Multifarious pretreatment strategies for the lignocellulosic substrates for the generation of renewable and sustainable biofuels: A review
2020
Abstract Currently major part of the world’s energy requirements is fulfilled by fossil resources. Severe economic and environmental problems along with their limited resources are still a major issue. Long-term environmental and commercial concern has focussed into huge research in the past decades to replace fossil fuels with renewable sources of energy. The main focus of energy research is lignocellulosic substrates, which seems to be the best for energy application due to easily availability, cost-effective and environment favourable production process. Therefore, lignocellulosic materials provide economical, environmental and energetic benefits with an alternative to traditional or hig…
Spontaneous domain formation of phospholipase A2 at interfaces: fluorescence microscopy of the interaction of phospholipase A2 with mixed monolayers …
1992
Abstract Fluorescence microscopy has recently been proven to be an ideal tool to investigated the specific interaction of phospholipase A 2 with oriented substrate monolayers. Using a dual labeling technique, it could be shown that phospholipase A 2 can specifically attack and hydrolyze solid analogous l -α-DPPC domains. After a critical extent of monolayer hydrolysis the enzyme itself starts to aggregate forming regular shaped protein domains (Grainger et al. (1990) Biochim. Biophys. Acta 1023. 365–379). In order to confirm that the existence of hydrolysis products in the mononlayer is necessary for the observed aggregation of phospholipase A 2 , mixed monolayers of d - and l -α-DPPC, l -α…
Stereochemical features of the hydrolysis of 9,10-epoxystearic acid catalysed by plant and mammalian epoxide hydrolases
2002
cis-9,10-Epoxystearic acid was used as a tool to probe the active sites of epoxide hydrolases (EHs) of mammalian and plant origin. We have compared the stereochemical features of the hydrolysis of this substrate catalysed by soluble and membrane-bound rat liver EHs, by soluble EH (purified to apparent homogeneity) obtained from maize seedlings or celeriac roots, and by recombinant soybean EH expressed in yeast. Plant EHs were found to differ in their enantioselectivity, i.e. their ability to discriminate between the two enantiomers of 9,10-epoxystearic acid. For example, while the maize enzyme hydrated both enantiomers at the same rate, the EH from soybean exhibited very high enantioselecti…
Acid‐Cleavable Poly(ethylene glycol) Hydrogels Displaying Protein Release at pH 5
2020
Abstract PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (M n) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG‐co‐isoEPB)MA copolymer and the hydrogels showed pH‐…
Spectrophotometric determination of ethiofencarb in waters by reaction with p-aminophenol
1993
An automatized procedure has been developed for the spectrophotometric determination of ethiofencarb in water by reaction with p-aminophenol after alkaline hydrolysis to obtain the corresponding phenol sulphone. The hydrolyzed samples are continuously introduced into different manifolds at the same time as 300 mg/l p-aminophenol, 0.004 mol/l KIO4 and 0.04 mol/l NaOH solutions. The absorbance is measured at 638 nm after a reaction time of 6 min in stop flow. This absorbance band corresponds to the indo dye obtained from the reaction between the phenol sulphone of ethiofencarb and the quinoneimine form of the p-aminophenol and it permits a matrix-free spectrophotometric determination of ethio…
The N-terminal domain of the light-harvesting chlorophyll a/b-binding protein complex (LHCII) is essential for its acclimative proteolysis.
2000
AbstractVariations in the amount of the light-harvesting chlorophyll a/b-binding protein complex (LHCII) is essential for regulation of the uptake of light into photosystem II. An endogenous proteolytic system was found to be involved in the degradation of LHCII in response to elevated light intensities and the proteolysis was shown to be under tight regulation [Yang, D.-H. et al. (1998) Plant Physiol. 118, 827–834]. In this study, the substrate specificity and recognition site towards the protease were examined using reconstituted wild-type and mutant recombinant LHCII. The results show that the LHCII apoprotein and the monomeric form of the holoprotein are targeted for proteolysis while t…
Metabolic shift of polyphosphate-accumulating organisms with different levels of polyphosphate storage
2012
Previous studies have shown that polyphosphate-accumulating organisms (PAOs) are able to behave as glycogen-accumulating organisms (GAOs) under different conditions. In this study we investigated the behavior of a culture enriched with Accumulibacter at different levels of polyphosphate (poly-P) storage. The results of stoichiometric ratios Gly degraded/HAc uptake, PHB synthesized/HAc uptake, PHV synthesized/HAc uptake and P release/HAc uptake confirmed a metabolic shift from PAO metabolism to GAO metabolism: PAOs with high poly-P content used the poly-P to obtain adenosine tri-phosphate (ATP), and glycogen (Gly) to obtain nicotinamide adenine dinucleotide (NADH) and some ATP. In a test whe…