Oncology & Cancer

Vitamin B6, leukemia's deadly addiction

Scientists have discovered that Acute Myeloid Leukemia (AML) grows by taking advantage of the B6 vitamin to accelerate cell division. The research team from Cold Spring Harbor Laboratory (CSHL) and Memorial Sloan Kettering ...


Experimental therapy may offer hope for rare genetic disorders

Researchers at Massachusetts General Hospital (MGH) have developed a new way to alleviate problems caused by dysfunctional mitochondria, which are the "powerhouses" that produce energy in cells. Their discovery, reported ...

Medical research

Saccharin derivatives give cancer cells a not-so-sweet surprise

Saccharin received a bad rap after studies in the 1970s linked consumption of large amounts of the artificial sweetener to bladder cancer in laboratory rats. Later, research revealed that these findings were not relevant ...

Medical research

Study examines HIV drug's potential to treat Alzheimer's

A drug used to treat and prevent HIV/AIDS is showing promise as a potential therapy for Alzheimer's disease, and Vanderbilt University biochemist F. Peter Guengerich, Ph.D., is aiding efforts to make this approach to improving ...

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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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