Medications

Clinical trial suggests Parkinson's drug is safe in humans

A large team of researchers from Denali Therapeutics, working with colleagues from multiple entities in the U.S. and one in Canada, has found that a LRRK2 inhibitor called DNL201 showed no ill effects to volunteers in a clinical ...

Diseases, Conditions, Syndromes

Coronary heart disease risk higher with COPD

Patients with chronic obstructive pulmonary disease (COPD) are more likely to have coronary heart disease (CHD), but no specific phenotypes have a higher risk, according to a study published online April 27 in PLOS ONE.

Overweight & Obesity

Scientists study links between obesity, age and body chemistry

A team of Clemson University scientists is making inroads in understanding the relationship between certain enzymes that are normally produced in the body and their role in regulating obesity and controlling liver diseases.

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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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