Diazonium inactivation in simultaneous-coupling and product inhibition in post-coupling azo-techniques for demonstrating activity of acid hydrolases

1984 ◽  
Vol 80 (2) ◽  
pp. 187-192 ◽  
Author(s):  
A. E. F. H. Meijer ◽  
A. H. T. Vloedman
Keyword(s):  
Product Inhibition ◽  
Acid Hydrolases ◽  
Post Coupling

scholarly journals Qualitative Properties of Autocatalytic Reactions Occurring in a Flow System

1985 ◽  
Vol 40 (7) ◽  
pp. 736-747
Author(s):  
Sang H. Kim ◽  
Vladimir Hlavacek
Keyword(s):  
Chaotic Behavior ◽  
Flow System ◽  
Cell Model ◽  
Dispersion Model ◽  
Travelling Waves ◽  
Continuous Model ◽  
Product Inhibition ◽  
Stable Node ◽  
Qualitative Properties ◽  
Intermediate Value

The dynamic behavior of an autocatalytic reaction with a product inhibition term is studied in a flow system. A unique steady state exists in the continuous tank reactor. Linear stability analysis predicts either a stable node, a focus or an unstable saddle-focus. Sustained oscillations around the unstable focus can occur for high values of the Damköhler number (Da). In the distributed system, travelling, standing or complex oscillatory waves are detected. For a low value of Da, travelling waves with a pseudo-constant pattern are observed. With an intermediate value of Da, single or multiple standing waves are obtained. The temporal behavior indicates also the appearance of retriggering or echo waves. For a high value of Da, both single peak and complex multipeak oscillations are found. In the cell model, both regular oscillations near the inlet and chaotic behavior downstream are observed. In the dispersion model, higher Peclet numbers (Pe) eliminate the oscillations. The spatial profile shows a train of pulsating waves for the discrete model and a single pulsating or solitary wave for the continuous model.

scholarly journals The Mechanism of End Product Inhibition of Serine Biosynthesis

1974 ◽  
Vol 249 (5) ◽  
pp. 1348-1355
Author(s):  
Ilga Winicov ◽  
Lewis I. Pizer
Keyword(s):  
Product Inhibition ◽  
Serine Biosynthesis

In vitro Action of Gastric Mucosal Lysosomal Enzymes on Intracellular Gastric Glycoproteins

1979 ◽  
Vol 34 (1-2) ◽  
pp. 90-95 ◽  
Author(s):  
Fouad M. Fouad ◽  
D. Waldron-Edward
Keyword(s):  
Cell Wall ◽  
Lysosomal Enzymes ◽  
Gastric Ulceration ◽  
Mucosal Cell ◽  
Gastric Lesions ◽  
Acid Hydrolases ◽  
Gastric Mucosal Cells ◽  
Mucosal Cells ◽  
Specific Increase

Abstract The results show that incubation of gastric mucosal cells from rat at pH ~4.5 or in the presence of aspirin is associated with a specific increase in the activity of some acid-hydrolases. Intracellular glycoproteins, isolated by non-degradative techniques from rat or dog fundic mucosal cells, were found to be potential bio-substrates for these acid-hydrolyses. This may suggest that cleavage of the carbohydrate moieties of the intracellular and mucosal cell wall glycoproteins is a fundamental step in the development of gastric ulceration. A model for gastric lesions is proposed and discussed in the light of the results obtained.

scholarly journals Effects of antimycin A and 2-deoxyglucose on secretion in human platelets. Differential inhibition of the secretion of acid hydrolases and adenine nucleotides

1979 ◽  
Vol 182 (2) ◽  
pp. 413-419 ◽  
Author(s):  
Holm Holmsen ◽  
Linda Robkin ◽  
H. James Day
Keyword(s):  
Shape Change ◽  
Adenine Nucleotides ◽  
Human Platelets ◽  
Dense Granule ◽  
Metabolic Inhibitors ◽  
Antimycin A ◽  
Acid Hydrolase ◽  
Acid Hydrolases ◽  
Dense Granule Secretion ◽  
Granule Secretion

1. Shape change, aggregation and secretion of dense-granule constituents in platelets differ in their dependence on cellular energy metabolism. The possibility that such a difference also exists between secretion of dense-granule constituents and acid hydrolases was investigated. 2. Human platelets were incubated with [14C]adenine in plasma, and then washed and resuspended in salt solutions. The effects of incubating the cells with antimycin A and 2-deoxyglucose on the concentrations of [14C]ATP, ADP, AMP, IMP and inosine plus hypoxanthine and on thrombin-induced secretion of ATP plus ADP and acid hydrolases were studied. The metabolic inhibitors only affected 14C-labelled nucleotides, whereas thrombin only liberated unlabelled ATP and ADP. 3. The extent of secretion decreased progressively with time during incubation with the metabolic inhibitors. At any time the secretion of acid hydrolases, β-N-acetylglucosaminidase, β-glucuronidase and β-galactosidase was inhibited to a greater extent than secretion of ATP plus ADP (dense-granule secretion). 4. Incubation with the metabolic inhibitors shifted the log (dose)–response relationship to higher thrombin concentrations, and with a greater shift for acid hydrolase secretion than for dense-granule secretion. 5. Antimycin, when present alone, caused a marked decrease in the rate of acid hydrolase secretion, but had no effect on dense-granule secretion. 6. These results further support the view that acid hydrolase secretion and dense-granule secretion are separate processes with different requirements for ATP energy. Acid hydrolase secretion, but not dense-granule secretion, appears to depend on a simultaneous rapid generation of ATP, which can be accomplished by oxidative, but not by glycolytic, ATP production.

scholarly journals Product inhibition studies on bovine liver carbamoyl phosphate synthetase

1974 ◽  
Vol 141 (3) ◽  
pp. 817-824 ◽  
Author(s):  
Keith R. F. Elliott ◽  
Keith F. Tipton
Keyword(s):  
Inorganic Phosphate ◽  
Substrate Binding ◽  
Inorganic Ions ◽  
Bovine Liver ◽  
Product Inhibition ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate ◽  
Product Release ◽  
Proposed Model ◽  
Inhibition Studies

A study of the product-inhibition patterns of carbamoyl phosphate synthetase from bovine liver is reported. Inhibition by adenosine, AMP and inorganic ions is also reported. The results are in agreement with the previously proposed model in which the order of substrate binding is ATPMg, followed by HCO3−, ATPMg and NH4+. The order of product release on the basis of the reported results is carbamoyl phosphate, followed by ADPMg, ADPMg and inorganic phosphate.

Structure-activity relations and β-lactamase resistance

1980 ◽  
Vol 289 (1036) ◽  
pp. 197-205 ◽  
Keyword(s):  
Broad Spectrum ◽  
Product Inhibition ◽  
Sulphur Atom ◽  
Chemical Modifications ◽  
Gram Negative ◽  
Structure Activity ◽  
Broad Spectrum Resistance ◽  
Structure Activity Relations ◽  
Minor Influence ◽  
A Minor

β-Lactam antibiotics resistant to β-lactamase degradation can be produced by many chemical modifications, but often at the expense of antibacterial activity. Substitution onto several positions in the molecule produces different and often selective resistance; for instance, heavily sterically hindered acyl groups give staphylococcal P-lactamase resistance to penicillins, and resistance to some enzymes from Gram-negative pathogens to both penicillins and cephalosporins. 6-α- or 7-α-substituents respectively confer a broad spectrum of resistance (e.g. cefoxitin), but changes at positions 2 or 3 have only a minor influence on enzyme susceptibility. Changes in the ring condensed with the β-lactam, such as changing ceph-3-em to ceph-2-em may greatly enhance stability. Small improvements can occur when the nuclear sulphur atom is oxidized, but a much better effect is obtained when it is replaced by another atom such as oxygen, as in clavulanic acid. This compound appears to have broad spectrum resistance which is actually due to susceptibility and subsequent product inhibition.

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