Structural Biochemistry/Enzyme Catalytic Mechanism/Hydrolysis
Hydrolysis is the process of a water reaction. It means to break using water. Hydrolysis comes from the Greek work hydro meaning water; and lysis meaning break. This occurs through a water molecule cleaving into two parts of a molecule; one molecule will get the H+ ion, while the other part of the molecule receives the OH- group. Hydrolysis reaction is used to break down polymers into monomers.
Hydrolysis is important for plants and animals in order for them to sustain life. This process helps to make energy for metabolism and storage. All of this is needed for biosynthesis of small molecules, as well as, active transport of molecules across the cellular membrane. It is also used in oxidation reaction and ATP.
Hydrolysis reactions help the catalysis reaction in living organisms by a class of enzymes known as hydrolases. The biochemical reactions that break down polymers such as proteins (peptide bonds between amino acids), nucleotides, complex sugars and starch, and fats are catalyzed by this class of enzymes. Within this class, lipases, amylases and proteinases hydrolyze fats, sugars and proteins, respectively.
Cellulose-degrading bacteria and fungi play a special role in paper production and other everyday biotechnology applications, because they have enzymes (cellulases and esterases) that can break cellulose into polysaccharides (polymers of sugar molecules) or glucose, and break down stickies.
Enzymes accelerate reactions by lower the activation energy required for the reaction. They play very important roles in the biological world. Proteolysis enzymes are one of the classes of enzymes which are very specific. The mechanism of proteolytic enzyme catalyze proteolysis is showed below:
Cleavage of peptide bonds between amino acids are made by hydrolysis. Water is activated by a protease to instigate the reaction. The hydroxyl ion from the water acts as a neucleophile and attacks the carbon of the carbonyl group of the ester or amide. In an aqueous base, hydroxyl ions are better nucleophiles than dipoles such as water. In acid, the carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups.
Moreover, hydrolysis is an important process in plants and animals because of its use in energy metabolism and storage. The energy storing molecule, adenosine triphosphate (ATP)contains pyrophosphate linkages (bonds formed when two phosphate units are combined together) that release energy when the pyrophosphate bonds are broken. Hydrolysis is used in order to break these bonds. ATP can undergo hydrolysis in two ways: the removal of terminal phosphate to form adenosine diphosphate (ADP) and inorganic phosphate, or the removal of a terminal diphosphate to yield adenosine monophosphate (AMP) and pyrophosphate.
Furthermore, most biochemical reactions use catalytic actions to instigate hydrolysis of proteins, fats, oils, and carbohydrates to be broken down into their monomers for processing and energy. For example, microbes employ cellulosomes, a multienzyme complex containing hemicellulase, cellulase, and even pectinase, to hydrolyze plant cell walls made up of polysaccharides and release energy. Currently there is research in transforming cellulosic biomass into sugar, which can then be transformed into a viable energy source such as ethanol. However, breaking down the cellulose from the biomass is difficult to do in the lab and requires a variety of enzymes working in sync. Understanding how cellulosomes do their work might just be the key to solving the energy crisis.
Another example of hydrolysis within our body is our digestive system. The material we eat, food, comes into our body in the form of polymer. The food is too large to enter our cells. As the food enters our digestive tracts, various enzymes work to break down the food (polymer), which in turn will speed up hydrolysis. The resulting monomers will be small enough to be absorbed into our bloodstream to be distributed to all the cells in our body. Those cells can then perform dehydration reactions, the opposite of hydrolysis, to take those monomers to form new and different polymers that can be used as other specific functions in the body.
Berg, Jeremy M. "Biochemistry", Sixth Edition, W.H. Freeman and Company, N.Y., 2002
Fontes, C., Gilbert, H., (2010, April 7). Cellulosomes: Highly Efficient Nanomachines Designed to Deconstruct Plant Cell Wall Complex Carbohydrates. Annual Review of Biochemistry, 79, 655-681. Retrieved October 22, 2010 from www.annualreviews.org.