Related topics: protein · cells · bacteria · chemical reactions · cancer

Surprising enzymes found in giant ocean viruses

A new study led by researchers at Woods Hole Oceanographic Institution (WHOI) and Swansea University Medical School furthers our knowledge of viruses—in the sea and on land— and their potential to cause life-threatening ...

Molecular scissors stabilize the cell's cytoskeleton

Researchers at the Paul Scherrer Institute PSI in Villigen, Switzerland, have for the first time elucidated the structure of important enzymes in human cells that alter essential building blocks of the cellular cytoskeleton. ...

Artificial muscles powered by glucose

Artificial muscles made from polymers can now be powered by energy from glucose and oxygen, just like biological muscles. This advance may be a step on the way to implantable artificial muscles or autonomous microrobots powered ...

Construction kit for custom-designed products

Microorganisms often assemble natural products similar to product assembly lines. Certain enzymes, non-ribosomal peptide synthetases (NRPS), play a key role in this process. Biotechnologists at Goethe University have now ...

Scientists uncover binding secret behind protein 'superglue'

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have pinpointed how a special class of plant-derived enzymes, known as peptide ligases, work to join proteins together. Such binding is an important ...

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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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