OpenStax Biology 2e
For many years, scientists thought that enzyme-substrate binding took place in a simple “lock-and-key” fashion. This model asserted that the enzyme and substrate fit together perfectly in one instantaneous step. However, current research supports a more refined view scientists call induced fit. This model expands upon the lock-and-key model by describing a more dynamic interaction between enzyme and substrate. As the enzyme and substrate come together, their interaction causes a mild shift in the enzyme’s structure that confirms an ideal binding arrangement between the enzyme and the substrate’s transition state. This ideal binding maximizes the enzyme’s ability to catalyze its reaction.– When glucose comes close to the hexokinase active site, it induces a conformational shift in the enzyme to better hold the substrate glucose. This hypothesis is known as what?
When an enzyme binds its substrate, it forms an enzyme-substrate complex. This complex lowers the reaction’s activation energy and promotes its rapid progression in one of many ways. On a basic level, enzymes promote chemical reactions that involve more than one substrate by bringing the substrates together in an optimal orientation. The appropriate region (atoms and bonds) of one molecule is juxtaposed to the other molecule’s appropriate region with which it must react. Another way in which enzymes promote substrate reaction is by creating an optimal environment within the active site for the reaction to occur. Certain chemical reactions might proceed best in a slightly acidic or non-polar environment. The chemical properties that emerge from the particular arrangement of amino acid residues within an active site create the perfect environment for an enzyme’s specific substrates to react.– What enzyme catalyzes the same reaction but their physical and chemical properties exhibit significant differences?
You have learned that the activation energy required for many reactions includes the energy involved in manipulating or slightly contorting chemical bonds so that they can easily break and allow others to reform. Enzymatic action can aid this process. The enzyme-substrate complex can lower the activation energy by contorting substrate molecules in such a way as to facilitate bond-breaking, helping to reach the transition state. Finally, enzymes can also lower activation energies by taking part in the chemical reaction itself. The amino acid residues can provide certain ions or chemical groups that actually form covalent bonds with substrate molecules as a necessary step of the reaction process. In these cases, it is important to remember that the enzyme will always return to its original state at the reaction’s completion. One of enzymes’ hallmark properties is that they remain ultimately unchanged by the reactions they catalyze. After an enzyme catalyzes a reaction, it releases its product(s).Research from the University of Illinois and the University of California, Davis has chemists one step closer to recreating nature’s most efficient machinery for generating hydrogen gas. This new development may help clear the path for the hydrogen fuel industry to move into a larger role in the global push toward more environmentally friendly energy sources. Currently, hydrogen gas is produced using a very complex industrial process that limits its attractiveness to the green fuel market, the researchers said. In response, scientists are looking toward biologically synthesized hydrogen, which is far more efficient than the current human-made process, said chemistry professor and study co-author Thomas Rauchfuss. Biological enzymes, called hydrogenases, are nature’s machinery for making and burning hydrogen gas. These enzymes come in two varieties, iron-iron and nickel-iron – named for the elements responsible for driving the chemical reactions. The new study focuses on the iron-iron variety because it does the job faster, the researchers said.
Clark, M., Douglas, M., Choi, J. Biology 2e. Houston, Texas: OpenStax. Access for free at: https://openstax.org/details/books/biology-2e