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Substrate (chemistry)

About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.


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Journal ArticleDOI
TL;DR: Rates of enzymic attack on various substrates indicated that the nitrilase has a fairly broad specificity and that the fungus probably plays an important role in the biodegradation of certain nitrilic herbicides in the environment.
Abstract: 1. A strain of the fungus Fusarium solani able to use benzonitrile as sole source of carbon and nitrogen was isolated by elective culture. 2. Respiration studies indicate that the nitrile, after degradation to benzoate, is catabolized via catechol or alternatively via p-hydroxybenzoate and 3,4-dihydroxybenzoate. 3. Cell-free extracts of benzonitrile-grown cells contain an enzyme mediating the conversion of benzonitrile into benzoate and ammonia. 4. The nitrilase enzyme was purified by DEAE-cellulose chromatography, (NH4)2SO4 precipitation and gel filtration on Sephadex G-200. The homogeneity of the purified enzyme preparation was confirmed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and isoelectric focusing on polyacrylamide gel. 5. The enzyme showed a broad pH optimum between pH7.8 and 9.1 and a Km with benzonitrile as substrate of 0.039mm. The activation energy of the reaction deduced from an Arrhenius plot was 48.4kJ/mol. 6. The enzyme was susceptible to inhibition by thiol-specific reagents and certain heavy metal ions. 7. Gel filtration gave a value of 620000 for the molecular weight of the intact enzyme. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis demonstrated that the enzyme was composed of eight subunits of mol.wt. 76000. 8. Rates of enzymic attack on various substrates indicated that the nitrilase has a fairly broad specificity and that the fungus probably plays an important role in the biodegradation of certain nitrilic herbicides in the environment.

155 citations

Journal ArticleDOI
TL;DR: The fluorescent assay for angiotensin-I converting enzyme was adequate for the study of ACE inhibition by captopril and several peptides and it also showed a very good correlation with a well-established method.

155 citations

Journal ArticleDOI
TL;DR: The kinetics of ammonia oxidation and the ability of a marine ammonia-oxidizing bacterium, Nitrosococcus oceanus, to metabolize methane were investigated in semicontinuous batch culture and inhibitors and coreactants were determined in order to elucidate the behavior of the ammonia oxygenase enzyme in N. oceanus.
Abstract: The kinetics of ammonia oxidation and the ability of a marine ammonia-oxidizing bacterium, Nitrosococcus oceanus, to metabolize methane were investigated in semicontinuous batch culture. The effects of inhibitors (acetylene and nitrapyrin) and coreactants were determined in order to elucidate the behavior of the ammonia oxygenase enzyme in N. oceanus. Acetylene and nitrapyrin were potent inhibitors and their effects were not mitigated by increased ammonia concentrations. Oxygen concentration had the effect of a mixed-type inhibitor; reduced oxygen inhibited the rate or ammonia oxidation at high substrate concentration but may enhance the rate at low substrate concentrations. Substrate affinity in terms of NH 4 + increased (K m decreased) with increasing pH. Optimal pH was about 8. Methane inhibited ammonia oxidation; the interaction was not simple competitive inhibition and the presence of multiple active sites on the enzyme was indicated by the behaviour of the inhibited treatments. Half-saturation constants for methane (K i=6.6 μM) and ammonia (K m=8.1 μM) were similar. N. oceanus oxidized methanol and methane linearly over time, with CO2 and cell material being produced at approximately equal rates.

155 citations

Journal ArticleDOI
TL;DR: Two distinctly different steps precede rapid hydrolysis of dipalmitoylphosphatidylcholine small unilamellar vesicles by pancreatic phospholipase A2: a Ca2+-independent binding of the enzyme to the substrate vesicle, which for chemically pure bilayers occurs best in the gel phase, and at least one of these two steps appears to involve enzyme-enzyme interaction.

155 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202214
2021807
20201,053
20191,064
20181,112
20171,024