Medical research

Stressing cancer with spice

A new study by scientists in Japan and Indonesia reports how an experimental drug agent stops cancer cells from growing. A little over a decade ago, Indonesian scientists first reported pentagamavumon-1 (PGV-1), an analogue ...

Medical research

Cancer cells can reuse apparent 'dead end metabolites'

Researchers at Winship Cancer Institute of Emory University have discovered that an apparent "dead end metabolite" has a previously unknown function regulating cell growth. The finding could guide efforts to target cancer ...

Medications

FDA approves drug for most deadly form of tuberculosis

(HealthDay)—A new drug has been approved as part of a powerful, three-pronged treatment regimen for the most deadly strain of tuberculosis, the U.S. Food and Drug Administration announced Wednesday.

Medical research

Antibiotics through machine learning

Machine learning techniques can be used to search for new drugs for one of the most insidious causes of stomach ulcers and other gastrointestinal problems, the bacteria known as Helicobacter pylori.

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Enzyme

Enzymes are biomolecules that catalyze (i.e., increase the rates of) chemical reactions. Nearly all known enzymes are proteins. However, certain RNA molecules can be effective biocatalysts too. These RNA molecules have come to be known as ribozymes. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at significant rates. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.

Like all catalysts, enzymes work by lowering the activation energy (Ea or ΔG‡) for a reaction, thus dramatically increasing the rate of the reaction. Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions. As with all catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter the equilibrium of these reactions. However, enzymes do differ from most other catalysts by being much more specific. Enzymes are known to catalyze about 4,000 biochemical reactions. A few RNA molecules called ribozymes catalyze reactions, with an important example being some parts of the ribosome. Synthetic molecules called artificial enzymes also display enzyme-like catalysis.

Enzyme activity can be affected by other molecules. Inhibitors are molecules that decrease enzyme activity; activators are molecules that increase activity. Many drugs and poisons are enzyme inhibitors. Activity is also affected by temperature, chemical environment (e.g., pH), and the concentration of substrate. Some enzymes are used commercially, for example, in the synthesis of antibiotics. In addition, some household products use enzymes to speed up biochemical reactions (e.g., enzymes in biological washing powders break down protein or fat stains on clothes; enzymes in meat tenderizers break down proteins, making the meat easier to chew).

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