catalase?
Catalases are proteins that act as enzymes by speeding up the breakdown of hydrogen peroxide in the body. They, like other proteins, consist of one or more chains of amino acids linked together by peptide bonds and the sequence of these amino acids determine the unique 3D conformation in which the chains are folded. Since this conformation is vital for the activity of the enzyme, it is stabilized by relatively weak interactions of amino acids in different parts of the peptide chains with each other and with the surrounding medium. Disruptions to these interactions caused by high temperatures, acidic or basic conditions, or changes in the polarity of the medium lead to denaturation, or the unfolding of the peptide chains, which ultimately results in the loss of enzymatic activity, solubility, as well as other properties than an enzyme would have if its chains were actually folded properly.
The study of the rate at which an enzyme works (enzyme kinetics) has found that an enzyme’s “speed” is influenced by many factors, namely the substrate concentration (hydrogen peroxide in the case of a catalase), temperature, the concentration of the enzyme, pH levels, and the presence of inhibitors. The peak of an enzyme’s activity is reached when these factors are in their optimal range, and decreases in enzymatic activity are generally apparent once the enzyme is exposed to conditions that are outside its optimal range.
Substrate Concentration: Under constant conditions, the rate of enzymatic reaction should escalate with increasing concentrations of substrate. However, the above concept does not apply to excessively high substrate concentrations, where low values of substrate accelerate and high values retard the reaction rate. Once the maximum rate for that reaction is eventually reached, however, additional increases in the substrate concentration will have no effect whatsoever.
Temperature: In general, chemical reactions accelerate as temperature increases as more of the reacting molecules have the kinetic energy necessary to undergo the reaction. Enzyme catalyzed reactions also tend to go faster with rising temperatures until a temperature optimum is reached and temperatures beyond this optimum result in the disruption of enzyme’s conformation.
pH: pH, or the measure of the hydrogen ion concentration of a solution, is generally measured on a scale of 0-14 with values below 7 being acidic, values above 7 being basic, and a value of 7 being neutral. Enzymes typically gain hydrogen ions from acidic solutions and lose them to basic ones and therefore undergo a change in conformation that decreases enzyme activity whenever they are exposed to an environment not within their optimum pH range. The pH optimum for some enzymes can vary from a broad range to a narrow pH optimum, but it is mostly affected by the substrate being used and other experimental conditions.
Salt Concentration: Every enzyme has an optimal salt concentration in which it can work best. reaction. A salt concentration which is too high or too low will denature the enzyme.
Presence of Inhibitors: An inhibitor is a molecule that interacts with an enzyme to reduce its activity. Enzyme inhibitors change the catalytic action of the enzyme to slow or stop catalysis and three common types of enzyme inhibition include competitive, non-competitive, and substrate inhibition.
When the substrate and a substance resembling the substrate are added to the enzyme, competitive inhibition occurs because of the lock-key theory of enzyme catalysts. The theory, which utilizes the idea of ‘an active site’ (in the case of catalase, the active site is the hemp group), explains that normally, one particular portion of the enzyme surface has a strong attraction to the substrate so that it is held in a way that makes favourable its conversion to the reaction product. However, an inhibitor resembling the substrate will compete with the substrate for the position of the enzyme lock, but will be unable to open the lock to complete the reaction when it wins the position. Therefore, the reaction is slowed down as some of the vacant enzyme sites have been taken by the inhibitor molecules rather than substrate molecules. On the other hand, if a dissimilar substance which does not fit the site is present, the enzyme simply rejects it, accepts the substrate, and the reaction proceeds normally.
Non-competitive inhibition occurs when the inhibitor binds somewhere other than the active site of the enzyme causing a change in the shape of the enzyme molecule so that the substrate molecule can no longer bind to the active site. An example of a noncompetitive inhibitor is copper sulphate. Cyanide is an example of a competitive inhibitor because it binds to the active site in the enzyme molecule.
Substrate inhibition will sometimes occur when excessive amounts of substrate are present. Additional amounts of substrate added to the reaction mixture after the point actually decreases the reaction rate. This is due to the fact that there are so many substrate molecules competing for the active sites on the enzyme surfaces that they block the sites and prevent any other substrate molecules from occupying them.
Presence of Activators: An activator is a molecule that interacts with an enzyme and increases its activity.