Structure of Enzymes and Their Role in Metabolic Reactions - Assignment Example

Structure of Enzymes and Their Role in Metabolic Reactions Introduction: Enzymes represent large molecules within the body of human beings that enable increasing the rates of chemical reactions that occur in the body. They themselves do not undergo any change. Without the presence of the enzymes, the catalysis of the chemical reactions would not have been possible, since they serve as the biological catalysts in the reactions (Bettelheim et al, 2008, p.614). The metabolic reactions are essential in the body since they allow the human bodies to survive. Hence enzymes play a significant role in catalysis of these reactions without which the human bodies would work. The enzymes work by speeding up these vital reactions in the body (Starr & McMillan, 2008, p.59). Enzymes include three different categories – metabolic, digestive, and plant enzymes. The metabolic enzymes run the processes of the body, with damages and decays being repaired as well as diseases being healed. The digestive enzymes incorporate carbohydrates, proteins and fats that are required by the body. The enzymes from fresh plants enable digestion of food in the body, helping the digestive enzymes as well. Without enzymes, human beings would not be able to breathe, digest food or even move their muscles. The role of the enzymes cannot be performed by any other element present in the body, hence its importance in the body (Page, 1997, p.30). Enzyme and Its Role: Amylase: For this particular study, amylase has been selected, which is an enzyme available in the human body. The amylase enables the digestion of carbohydrates in the body. The pancreas and the glands that are generally responsible for the creation of saliva are also responsible for the production of amylases. With the inflammation of the pancreas, the amylases get released in the blood within the body (Amylase – blood, 2012). The amylases produced in the pancreas enable conversion of polysaccharides into disaccharide maltose. It is found in its active form. This is primarily because the secretory cells are not endangered when the amylases are in their active forms. Polysaccharides are not contained in these cells (Sherwood, 2008, p.614). The amylases may be of the salivary, the gastric, and the pancreatic. Salivary amylase is produced by salivary glands. Starch are the main targets of these enzymes that are broken down into maltose, that represent two glucose or sugar molecules that are in a bonded form. Gastric amylase targets those particles of starch that are remaining and enter the stomach. The pancreatic amylase proves to be essential allowing the digestion in the body (Wargolet, 2011). The figure beside represents the structure of salivary amylase as obtained in human bodies. There are 496 residues of amino acids present in amylase along with one calcium ion, one chloride ion and 170 molecules of water. The structure reflects a multidomain form that consists of three domains represented as A, B, and C. The A domain consists of a structure that is in a barrel shape. There is no specific topology for domain B, while domain C consists of a structure that is shaped as a Greek-key barrel. The pancreatic amylase is represented in the figure below that consists of different cleavage patterns. If their primary sequences are considered, they are highly homologous in form. Tests have revealed that there are 15 amino acid differences between the sequences available in the structure (My Favorite Protein: ?-amylase, n.d.). The structure of the amylases are quite different from the structure of hemoglobin that is a protein consisting of polypeptide subunits, four in number, that are held by ionic bonds, hydrogen bonds, hydrophobic interactions, and van der Waals forces. Also, there are heme pigments present in these subunits. The four subunits are two ?-globin chains and two ?-globin chains (Hemoglobin, n.d.). As far as the secondary structure of amylase is concerned, it has been obtained that the secondary structure of domain B of the enzymes varies with the different specificities of the enzyme. The starch hydrolases and associated enzymes contained in the ?-amylase family consist of varying specifications of the enzyme, around 20 in number (Janecek, Svensson & Henrissat, 1997, p.322). While the enzyme performs its activity within the body, when the bonding between the active site of the enzyme and the substrate occurs, the bonds that are involved in the process include the hydrogen bonds, and dipole-dipole interactions. The weak intermolecular forces that are also involved include the Van der Waals forces, Dispersion forces, or London forces (Enzymes, n.d.). Active Site of Amylase: The function of amylase occurs in an unpleasant environment in the intestine. The enzyme is small and stable in nature and has the capability to resist to unfavorable conditions. There are three acidic groups that are contained in the active site of amylase. These groups of acids are responsible for most of the work of the enzyme. Glutamate 233, aspartate 197, and aspartate 300 are the amino acids making up the active site of the amylase and hence function in combination enabling cleavage between the sugar molecules present in the starch chains. There are short chains of five units of sugar in the structure that are bound in the active site of the enzyme. A calcium ion is also present nearby that enables stabilization of the enzyme. A chloride ion can also be obtained that assists the enzyme in the catalysis of metabolic reactions in the body (Alpha-amylases, 2006). Pancreatic amylase is found to be active in the lumen that is a part of the small intestine in the body of humans. The enzyme has the capability to break down molecules of starch and glycogen. However it cannot break down plant polysaccharides like cellulose, primarily because of their fibrous nature. Thus these molecules that cannot be broken down in the small intestine cannot get digested here and instead have to move to the large intestine thereby providing most amount of the food. In general, the salivary and pancreatic amylases in their active states generate dextrin that is a compound containing glucose molecules in the form of short chains (McDowell, 2010, p.127). Human pancreatic alpha-amylase (HPA), HPA-AI03 is a pseudo-hexasaccharide that consists of a unit of acarviosine glucose attached to maltotirose. There is a polyhydroxylated aminocyclohexene derivative contained in the acarbose. HPA forms a complex with AI03 thus acting as an enzyme-inhibitor. The active site of the enzyme is V-shaped with a chloride ion present in the site. The reorganized creation for A103 builds added contact with HPA that in turn advocate that it is a further effective inhibitor. The rearrangement of the HPA with AI03 attaches firmly in the active site with a leg on each side of subsites -3 through +3. “The first step is the initial hydrolysis of AI03 to generate two main products: an acarbose-like structure and maltose. The second step is the elongation of the product derived from step 1. It can be condensed to a larger inhibitor derivative. AI03 itself is the most likely donor to the transglycosylation reaction due to the relatively high concentration. The third step is a final hydrolysis process” (Hunter, 2011). Activation Energy: In order to perform metabolic reactions in the body, molecules generally exist in a stable state and energy is required for the reactions to take place. However energy barriers often hinder the process of reaction. Activation energy refers to the amount of energy that is needed in order to overcome the energy barrier and enable the metabolic reaction to be completed (Kent, 2000, p.41). Human bodies are in need of continuous supply of energy for the different chemical reactions to occur within the body. 70 to 80 percent of the total energy that a human body gains is utilized in the basic functions performed in the body, including metabolism as one of the important functions (Chiras, 2011, p.91). When temperature is increased, the kinetic energy of the reaction rises and thus the collisions of the enzyme and the substrate increase, thus increasing the rate of the reaction. However, in order not to destroy the bonds and the reaction, the amount of temperature provided needs to be limited as well (Investigating the Effects of Amylase Concentration on the Breakdown of Starch, 2011). Environmental factors affecting the function of amylases: The breakdown of starch in the body depends on the amount and concentration of amylases and in the form they are altered. Since there is only one active site per enzyme present in the body, hence the enzymes can catalyze only one reaction at one point of time. This reflects the formation of only a single enzyme-substrate complex. Thus the rates of reactions increase with the increasing numbers of the enzymes (Investigating the Effects of Amylase Concentration on the Breakdown of Starch, 2011). There are various natural substances that have the ability to inhibit the activity of amylases. Wheat and white kidney beans, particularly the concentrated extracts if these molecules, have been obtained to be the main sources in this regard. The amylase inhibitors attach to the enzymes and hinder the enzymes from recognizing the starch molecules thus affecting the chemical reactions as well (What is an Amylase Inhibitor?, 2013). As far as the effect of temperature and pH is concerned, it has been obtained that with increase in temperature of the environment, the rates of reaction also increases (Teller, 2005). The optimum level of pH at which pancreatic amylase works best is 6.7 to 7.0 and for malt amylase the range is 4.6 to 5.2 (What Are the Effects of pH on Amylase?, 2013). Conclusion: The amylase enzyme also can be considered to have a significant role to play in the process of homeostasis. This is primarily because the endocrinal functions of the pancreas assist the maintenance of homeostasis in the body by regulating the level of glucose in the blood (Chiras, 2011, p.108). Thus the pancreatic amylase can be realized to have a role in this regard since it would enable the chemical reactions to be catalyzed and enhanced. Thus from the above study, it may be concluded that like different enzymes present in the human body, amylase too has significance in the way it allows and enhances metabolic reactions in the body, that are highly essential for the human bodies to survive. References Alpha-amylases (2006), RCSB, available at: http://www.rcsb.org/pdb/education_discussion/molecule_of_the_month/download/Alpha-amylase.pdf (accessed on January 15, 2013) Amylase – blood (2012), NLM, available at: http://www.nlm.nih.gov/medlineplus/ency/article/003464.htm (accessed on January 14, 2013) Bettelheim, F.A. (2008), Introduction to General, Organic and Biochemistry, Connecticut: Cengage Learning Chiras, D. 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