What are enzimes? And where can theybe found?

Answer 1

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Enzymes are proteins that accelerate, or catalyze, chemical reactions. In these reactions, the molecules at the beginning of the process are called substrates and the enzyme converts these into different molecules: the products. Almost all processes in the cell need enzymes in order to occur at significant rates. Since enzymes are extremely 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.

Enzymes are known to catalyze about 4,000 reactions.[1] However, not all biological catalysts are proteins, since some RNA molecules called ribozymes can also catalyze reactions. Enzymes are usually named according to the reaction they catalyze. Typically the suffix -ase is added to the name of the substrate (e.g., lactase is the enzyme that cleaves lactose) or the type of reaction (e.g., DNA polymerase forms DNA polymers).

Like all catalysts, enzymes work by providing an alternative path of lower activation energy for a reaction and dramatically accelerating its rate. Some enzymes can make their conversion of substrate to product occur many millions of times faster. For example, the reaction catalysed by orotidine 5'-phosphate decarboxylase will consume half of its substrate in 78 million years if no enzyme is present. However, when the decarboxylase is added, the same process takes just 25 milliseconds.[2] 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 by being much more specific.

Enzyme activity can be affected by other molecules. Inhibitors are molecules that decrease enzyme activity, and activators are molecules that increase activity. Drugs and poisons are often enzyme inhibitors.

Some enzymes are used commercially, for example, in the synthesis of antibiotics. In addition, some household cleaning products use enzymes to speed up chemical reactions (e.g., enzymes in biological washing powders break down protein or fat stains on clothes).

Etymology and history

As early as the late 1700s and early 1800s, the digestion of meat by stomach secretions[3] and the conversion of starch to sugars by plant extracts and saliva were known. However, the mechanism by which this occurred had not been identified.[4]

In the 19th century, when studying the fermentation of sugar to alcohol by yeast, Louis Pasteur came to the conclusion that this fermentation was catalyzed by a vital force contained within the yeast cells called "ferments", which were thought to function only within living organisms. He wrote that "alcoholic fermentation is an act correlated with the life and organisation of the yeast cells, not with the death or putrefaction of the cells."[5]

In 1878 German physiologist Wilhelm Kühne (1837–1900) coined the term enzyme, which comes from Greek ενζυμον "in leaven", to describe this process. The word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment used to refer to chemical activity produced by living organisms.

In 1897 Eduard Buchner began to study the ability of yeast extracts to ferment sugar despite the absence of living yeast cells. In a series of experiments at the University of Berlin, he found that the sugar was fermented even when there were no living yeast cells in the mixture.[6] He named the enzyme that brought about the fermentation of sucrose "zymase".[7] In 1907 he received the Nobel Prize in Chemistry "for his biochemical research and his discovery of cell-free fermentation".

Having shown that enzymes could function outside a living cell, the next step was to determine their chemical nature. Many early workers noted that enzymatic activity was associated with proteins, but several scientists (such as Nobel laureate Richard Willstätter) argued that proteins were merely carriers for the true enzymes and that proteins per se were incapable of catalysis. However, in 1926, James B. Sumner showed that the enzyme urease was a pure protein and crystallized it; Sumner did likewise for the enzyme catalase in 1937. The conclusion that pure proteins can be enzymes was verified definitively by Northrop and Stanley, who worked on the digestive enzymes pepsin (1930), trypsin and chymotrypsin. These three scientists were awarded the 1946 Nobel prize in Chemistry.[8]

This discovery that enzymes could be crystalised eventually allowed their structures to be solved by x-ray crystallography. This was first done for lysozyme, an enzyme found in tears, saliva and egg whites that digests the coating of some bacteria; the structure was solved by a group led by David Chilton Phillips and published in 1965.[9] This high-resolution structure of lysozyme marked the beginning of the field of structural biology and the effort to understand how enzymes work at an atomic level of detail.

Structures and mechanisms

The activities of enzymes are determined by their three-dimensional structure.[10]

Most enzymes are much larger than the substrates they act on, and only a very small portion of the enzyme (around 3–4 amino acids) is directly involved in catalysis.[11] The region that contains these catalytic residues, binds the substrate and then carries out the reaction is known as the active site. Enzymes can also contain sites that bind cofactors, which are needed for catalysis. Some enzymes also have binding sites for small molecules, which are often direct or indirect products or substrates of the reaction catalyzed. This binding can serve to increase or decrease the enzyme's activity, providing a means for feedback regulation.

Like all proteins, enzymes are made as long, linear chains of amino acids that fold to produce a three-dimensional product. Each unique amino acid sequence produces a unique structure, which has unique properties. Individual protein chains may sometimes group together to form a protein complex. Most enzymes can be denatured—that is, unfolded and inactivated—by heating, which destroys the three-dimensional structure of the protein. Depending on the enzyme, denaturation may be reversible or irreversible.

Answer 2

Enzymes are the biological catalysts which catalyses various chemical reaction taking place in the body. Almost all the reactions taking place in the body are very slow to occure without a catalysts, which increases their speed dramatically. Enzymes are those catalysts. Structuraly, enzymes are proteins. These can be found in any cell of the body. Previously, it was thought that only proteins can act as enzymes but recent researches has been shown that certain RNAs also work as enzymes.

Answer 3

Enzymes are proteins or protein / nucleic acid complexes which can act to speed up the rate of a specific chemical reaction. They can act on a particular compound to modify it in any number of different ways including to cleave it, add phosphate to it, add lipid to it, move its chemical groups around, attach it to another molecule, etc. The list of different known enzymatic activities is quite long.

Answer 4

Offal - i will't eat any of it. yet i stumble on olive oil yummy in simple terms with somewhat salt further, and that i know others discover it yucky. I additionally love black pudding, made ideally from pigs' blood, and others discover that yucky. And the 1st Mate loves garlic, which repels me at one hundred yards (or metres, or meters, as you pick).

Answer 5

There's a bounty of info on the web if you spell it right: "enzymes".

Good looking!

Answer 6

It's "enzymes" not enzimes. enzymes are catalyst.