See J. E. and E. T. Bell, Proteins and Enzymes (1988).
The Columbia Encyclopedia, s.v. “enzyme,” accessed March 16, 2013, http://www.credoreference.com/entry/columency/enzyme
So previously we had covered amino acids and their linkages, that is polypeptides bonds and the structures that are formed along with them. This Week we’ve moved on to a somewhat more exciting topic. ENZYMES!
Now this is a HUGE topic, but to help us along i came across a little article that could help us.
According to “Credo Reference” an enzyme, also known as a biological catalyst, accelerates the rate of a reaction without being permanently chemically changed. Enzymes achieve this phenomenon by providing a different reaction pathway for the reaction to occur, thus lowering the activation energy required for the reaction to take place.
Factors which affect the rate at which the enzyme work include specific temperature ranges, pH ranges. The efficiency of a particular enzyme can also be measured usually by a turnover rate, measuring the number of molecules of compound opon which the enzyme works per molecule of enzyme per second. A useful example given in the article was of Carbonic anhydrase which has a turnover rate of 106 for removal of carbon dioxide from the blood binding it to water. Thus this rate means that one molecule of the enzyme can cause a million molecules of carbon dioxide to react in one second.
Also briefly mentioned in the helpful post, is the occurence of denaturation, where a denatured enzyme refers to an enzyme which has been altered in its chemcial and physical structure, so much so that it can no longer serve its purpose. Once an enzyme loses its shape, it can no longer catalyze its reactions since enzymes are selective for the molecules upon which they act, known as substrate molecules. Most enzymes will react with a small group consisting of closely related chemical compounds, demonstrating absolute specificity, thus having one substrate molecule, appropriate for the reaction.
An interesting fact, about enzymes is that some require non protein molecules, not excluding coenzyme molecules. These nonprotein components which are tightly bound to the protein are also referred to as prosthetic groups.
The active site is known as the region on the enzyme where the catalytic event takes place. Prosthetic groups, as mentioned above are usually located there. The side-chain groups of amino acid residues make up the enzyme molecule also participating in the catalytic event.
Another example given is in the enzyme trysin which brings together a histidine residue from one section of the mlecule with glycine and serine residues from another. Conclusively the side chains of these residues in this particular geometric arrangement produce the active site which accounts for the enzyme’s reactivity.
One may ask the question: How can these enzymes be identified and classified? Well, through crystalization of the amino acid sequence, and X-ray crystallography.
The informative post also mentions enzyme deficiency, where a number of metabolic diseases are known to be caused by deficiencies or malfunctions of the enzyme. An example of this is in albinism, caused by the enzyme responsible for the production of cellular pigments.