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October, 2006
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Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.

Enzyme Activity- Concept

JoVE 10585

Biological Catalysts

All living organisms continuously perform numerous biochemical reactions to sustain their presence. Most of these reactions require an input of energy to start, which is called the activation energy. Catalysts are chemicals that lower the activation energy. Even though catalysts facilitate a chemical reaction, they are not consumed by it. This means a catalyst …

 Lab Bio

Enzyme Inhibition

JoVE 11004

Inhibitors are molecules that reduce enzyme activity by binding to the enzyme. In a normally functioning cell, enzymes are regulated by a variety of inhibitors. Drugs and other toxins can also inhibit enzymes. Some inhibitors bind to the enzyme’s active site, while others inhibit enzymatic activity by binding to other sites on the protein structure.

Competitive inhibitors occupy the active site of enzymes, making them unable to accommodate the substrate. However, sufficiently high concentrations of the substrate can outcompete the inhibitor; as a result, competitive inhibitors slow an enzymes initial reaction rate but do not impact the enzyme’s maximum rate. One example of a competitive inhibitor is the drug disulfiram, used to treat chronic alcoholism. When alcohol is ingested, it is normally converted to acetaldehyde, which is then converted to acetyl coenzyme A by acetaldehyde dehydrogenase. Disulfiram binds to and occupies the active site of acetaldehyde dehydrogenase, making the enzyme unable to perform this conversion. As a result, a patient taking disulfiram immediately begins to experience hangover-like symptoms, such as headache, thereby decreasing alcohol consumption. Noncompetitive inhibitors bind to distinct sites on the enzyme, away from the active site. These are called allosteric sites and when molecules bind to them, the shape of

 Core: Metabolism

Enzyme Activity - Prep Student

JoVE 10584

Investigating the Effect of pH and Temperature on Peroxidase Activity
To make the extraction buffer for the peroxidase enzyme, mix equal volumes of 0.1 M sodium phosphate monobasic and 0.1 molar sodium phosphate dibasic solutions to achieve a final volume of 500 mL.
Test the resulting solution using a pH meter. The mixture should be between a pH…

 Lab Bio

Hormonal Regulation

JoVE 10893

The renin-aldosterone system is an endocrine system which guides the renal absorption of water and electrolytes, thus managing blood pressure and osmoregulation. Activation of the system begins in the kidneys with a small cluster of cells adjacent to the afferent and efferent blood vessels of the renal corpuscle. As the nephrons are filtering blood, juxtaglomerular cells monitor blood pressure. If they detect a decrease in pressure, they release the hormone renin into the bloodstream. Circulating renin interacts with angiotensinogen, a precursor protein synthesized by the liver, to create angiotensin I. A final step cleaves angiotensin I into angiotensin II, a process achieved by angiotensin-converting enzyme, or ACE, which is released by the lungs. Angiotensin II temporarily increases blood pressure by contracting smaller blood vessels. It also induces the release of aldosterone from the adrenal cortex of the kidneys. Aldosterone directly stimulates the reabsorption of sodium and the excretion of potassium by the kidneys to maintain electrolyte balance. Moreover, circulating levels of aldosterone stimulate the release of antidiuretic hormone, or ADH, by the hypothalamus in the brain. Upon reaching the kidneys, ADH upregulates aquaporin channels in the nephrons which increase the water retention in the blood vessels. The combined effects of

 Core: Regulation and Excretion

Quantitative, Real-time Analysis of Base Excision Repair Activity in Cell Lysates Utilizing Lesion-specific Molecular Beacons

1Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, 2Hillman Cancer Center, University of Pittsburgh Cancer Institute, 3Department of Experimental Therapy, The Netherlands Cancer Institute, 4Department of Human Genetics, University of Pittsburgh School of Public Health

JoVE 4168


NMR-Based Activity Assays for Determining Compound Inhibition, IC50 Values, Artifactual Activity, and Whole-Cell Activity of Nucleoside Ribohydrolases

1Department of Chemistry, Adelphi University, 2Department of Chemistry, Washington University in St. Louis, 3Department of Chemistry, Boston University

JoVE 59928


A RAPID Method for Blood Processing to Increase the Yield of Plasma Peptide Levels in Human Blood

1Charité Center for Internal Medicine and Dermatology, Division General Internal and Psychosomatic Medicine, Charité Universitätsmedizin Berlin, Campus Benjamin Franklin, 2Department of Internal Medicine, Institute of Neurogastroenterology and Motility, Martin-Luther Hospital, Academic Teaching Institution of Charité Universitätsmedizin Berlin, 3Department of Hepatology and Gastroenterology, Molecular Cancer Research Center (MKFZ), Campus Virchow-Klinikum, Charité-Universitätsmedizin Berlin

JoVE 53959

 Immunology and Infection

High-throughput Screening for Broad-spectrum Chemical Inhibitors of RNA Viruses

1Unité de Génomique Virale et Vaccination, Virology Department, Institut Pasteur, CNRS UMR3569, 2Unité de Chimie et Biocatalyse, Biochemistry and Structural Biology Department, Institut Pasteur, CNRS UMR3523, 3Unité des Interactions Moléculaires Flavivirus-Hôtes, Virology Department, Institut Pasteur

JoVE 51222

 Immunology and Infection
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