An enzyme is a biological molecule that catalyzes a chemical reaction. Most enzymes are proteins and the word "enzyme" is often used to mean a protein enzyme, but some RNA molecules also have catalytic activity, and to differentiate them from protein enzymes, they are referred to as RNA enzymes or ribozymes.

Enzymes are essential for life because most chemical reactions in living cells would occur too slowly, or would lead to different products without enzymes.

Like all catalysts, enzymes work by providing an alternate pathway of lower energy for a reaction. This speeds up the reaction, sometimes making it many millions of times faster. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions nor do they alter the equilibrium of a reaction. However, enzymes do differ from most other catalysts in showing much higher levels of specificity.

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PLoS Medicine: New Articles

PLoS Medicine Issue Image | Vol. 6(6) June 2009
Tue, 30 Jun 2009 07:00:00 -0000
Clean water should be recognized as a human right. At the March 2009 United Nations meetings coinciding with the World Water Forum, a declaration that would recognize water as a basic human right was defeated. In this month's Editorial, the PLoS Medicine Editors argue that access to clean water should be declared a basic human right for three reasons. First, access to clean water can substantially reduce the global burden of disease caused by water-borne infections. Second, the privatization of water—as witnessed in Bolivia, Ghana, and other countries—has not effectively served the poor, who suffer the most from lack of access to clean water. Third, the prospect of global water scarcity—exacerbated by climate change, industrial pollution, and population growth—means that no country is immune to a water crisis.Image Credit: Rudhach at flickr.com
Seasonal Hunger: A Neglected Problem with Proven Solutions
Bapu Vaitla et al. Tue, 30 Jun 2009 07:00:00 -0000
Clean Water Should Be Recognized as a Human Right
Tue, 30 Jun 2009 07:00:00 -0000
Can We “Hedge” against the Development of Antiviral Resistance among Pandemic Influenza Viruses?
David K. Shay et al. Tue, 30 Jun 2009 07:00:00 -0000
David K. Shay and Benjamin Ridenhour discuss a modeling study predicting that stockpiling a secondary antiviral for use early in a flu pandemic can forestall resistance to the primary stockpiled drug.
Pralidoxime in Acute Organophosphorus Insecticide Poisoning—A Randomised Controlled Trial
Michael Eddleston et al. Tue, 30 Jun 2009 07:00:00 -0000
In a randomized controlled trial of individuals who had taken organophosphorus insecticides, Michael Eddleston and colleagues find that there is no evidence that the addition of the antidote pralidoxime offers benefit over atropine and supportive care.
What Is the Optimal Therapy for Patients with H5N1 Influenza?
Nicholas J. White et al. Tue, 23 Jun 2009 07:00:00 -0000
Nicholas White discusses optimal dosing of oseltamivir, Robert Webster and Elena Govorkova discuss combination antiviral therapy, and Timothy Uyeki discusses clinical care of patients with H5N1.

EurekAlert! - Biology

Study identifies how tamoxifen stimulates uterine cell growth and cancer
Thu, 02 Jul 2009 00:00:00 -0400
(University of California - San Francisco) University of California - San Francisco researchers have identified a new "feed-forward" pathway linking estrogen receptors in the membrane of the uterus to a process that increases local estrogen levels and promotes cell growth.
'Genetic arms race' between bacteria, viruses subject of stimulus grant
Thu, 02 Jul 2009 00:00:00 -0400
(Michigan State University) The oceans teem with microscopic bacteria that produce much of Earth's oxygen as they absorb carbon dioxide greenhouse gas. But fast-mutating viruses also populate the seas, attacking marine bacteria in an ages-old evolutionary arms race. A Michigan State University researcher will probe that ancient dynamic against the backdrop of environmental and climate change, and the pivotal role played by aquatic bacteria in maintaining the Earth's biological balance.
Learning from locusts
Thu, 02 Jul 2009 00:00:00 -0400
(Queen's University) A similarity in brain disturbance between insects and people suffering from migraines, stroke and epilepsy points the way toward new drug therapies to address these conditions.

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