There are many reasons why enzymes have such a high specificity. The first variable is an enzyme’s primary structure. A primary structure is just a combination of amino acids. There are twenty different amino acids that the primary structure can be created from. Every enzyme has a different order that the acids are placed in and each one has a different number or amino acids. The slightest change in this structure can affect a protein’s conformation and function.
The secondary structure is a regular, repeated, coiling and folding of a protein’s polypeptide backbone. This folding is stabilized by hydrogen bonds between peptide linkages. These sections of polypeptide chains are repeatedly coiled or folded into patterns that add to the protein’s overall conformation. There are two types of secondary structures. They are alpha helixes and beta pleated sheets. Alpha helixes are helical coils stabilized by a hydrogen bond between every fourth peptide bond. They are usually found in fibrous protein such as keratin and collagen. Beta pleated sheets are structures where two regions of the polypeptide chain lie parallel to each other. Again hydrogen bonds between the parts of the backbone in the parallel regions hold the structure together. The cores of many globular proteins are made of beta pleated sheets.
The Term Paper on Amino Acid Structure Proteins Polypeptide
... come together to form a quaternary structure. The primary structure of a protein is formed when amino acids are linked together in a specific ... polypeptide by cleavage of the peptide bond. Cleavage is also used to activate or inactivate enzymes such as those that are involved ... of the polypeptide protrude from either side of the beta-sheet plane. Also like the alpha helix, the location of the ...
The 3-D shape of a protein is otherwise known as the tertiary structure. Superimposed on the patterns of secondary structure is a protein’s tertiary structure, consisting of irregular contortions from bonding side chains of the various amino acids. There are many types of bonds that are found in this structure including hydrogen, ionic, hydrophobic interactions, and van der Waals interactions. Stronger bonds such as the disulfide bridges form from covalent bonds between side chains of cysteine pairs. The sulfur of one cysteine bonds to the sulfur of the seconds and the disulfide bridge fastens parts of the protein together. Once nonpolar amino acid side chains are close together, van der Waals attractions reinforce hydrophobic interactions. Meanwhile, hydrogen bonds between polar side chains also help stabilize tertiary structure.
The structure that results from interaction between and among several polypeptide chains are called Quaternary structures. Subunits that fit together tightly are sometimes found in globular proteins. Hemoglobin is an example of a globular protein with quaternary structure because it is made up of two kinds of polypeptide chains with two of each kind per molecule. Not all proteins have a quaternary structure.
Enzymes are very selective as to which reaction they will catalyze. This means that enzymes are highly specific. Catalysts are specific to a particular substrate and that depends on the three dimensional shape of it or its tertiary structure. A substrate is the substance an enzyme acts upon. Each substrate has a specific shape that will only fit into the active site of a particular enzyme. The active site is the restricted region of an enzyme that binds the substrate to the enzyme. It is usually a pocket or groove on the protein’s surface. There is one model called the lock and key. This is demonstrated by the substrate fitting exactly into the enzymes active site similar to how a key kits perfectly into the lock. This is because the key has a particular shape and is the only one that will turn the lock.
The Term Paper on The Effects of Ph and Salinity on Enzyme Function
... stated about pH, change all protein structures, especially secondary and tertiary structures. The concentrations of enzymes and substrates rely heavily on each ... a specific site on an enzyme, called the allosteric site, and change the enzymes shape so that it is either ... needed products are made. Allosteric enzymes, which are constructed from a few polypeptide chains, control the rates of reactions ...
This is comparable to how a substrate has a special shape and it is the only one that will fit into a particular enzyme’s active site. There is another model called the induced fit. This explains that the enzyme changes its shape slightly in order to grasp the substrate. This is related to how a baseball glove wraps around the ball in order to hold it in tight. The example below shows how the enzyme sucrase will break up sucrose but not lactose due to the shape of the substrate and active site. This sums up how the structural organization within proteins are responsible the specificity of an enzyme breaking down a substrate
