enzyme

Examples of enzyme in the following topics:

• Enzyme Catalysis

  • However, catalysts are also found in nature in the form of enzymes.
  • One model of enzyme mechanism is called the induced fit model.
  • This model proposes that the binding of the reactant, or substrate, to the enzyme active site results in a conformational change to the enzyme.
  • An enzyme catalyzes a biochemical reaction by binding a substrate at the active site.
  • List the five typical mechanisms used by enzymes to catalyze biological reactions

• Biomolecules

  • Coordination complexes are found in many biomolecules, especially as essential ingredients for the active site of enzymes.
  • They are an integral component of proteins, especially the class of proteins that can perform chemical reactions, called enzymes.
  • The transition metals, particularly zinc and iron, are often key components of enzyme active sites.
  • As with all enzymes, the shape of the active site is crucial.

• Manganese

  • The classes of enzymes that have manganese cofactors are very broad.
  • The Mn-SOD enzyme is probably one of the most ancient, as nearly all organisms living in the presence of oxygen use it to deal with the toxic effects of superoxide formed from the 1-electron reduction of dioxygen.

• The Secondary & Tertiary Structures of DNA

  • Once the double stranded DNA is exposed, a group of enzymes act to accomplish its replication.
  • Topoisomerase: This enzyme initiates unwinding of the double helix by cutting one of the strands.
  • Helicase: This enzyme assists the unwinding.
  • These enzymes also check for errors (roughly ten per billion), and make corrections.
  • Ligase: Small unattached DNA segments on a strand are united by this enzyme.

• Disaccharides

  • Some bacteria have beta-glucosidase enzymes that hydrolyze the glycosidic bonds in cellobiose and cellulose.
  • Infants have a digestive enzyme which cleaves the beta-glycoside bond in lactose, but production of this enzyme stops with weaning.

• RNA and Protein Synthesis

  • The original proposal that each gene controlled the formation of a single enzyme has since been modified as: one gene = one polypeptide.
  • Such enzymes are found in all cells and are an essential component of retroviruses (e.g.
  • Since these post-translational reactions are generally catalyzed by enzymes, it may be said: "Virtually every molecule in a cell is made by the ribosome or by enzymes made by the ribosome. "
  • Cross-linking of the peptide side chains is then effected by transpeptidase enzymes.
  • Finally, transpeptidase enzymes reform the peptide cross-links between the rows and layers of peptidoglycan making the wall strong.

• Iron

  • Iron, the active site of many redox enzymes, has many oxidation states, but ferrous (Fe2+) and ferric (Fe3+) are the most common.
  • Iron is also the metal used at the active site of many important redox enzymes dealing with cellular respiration, oxidation, and reduction in plants and animals.

• Titanium, Chromium, and Manganese

  • In biology, manganese(II) ions function as cofactors for a large variety of enzymes with many functions.
  • Manganese enzymes are particularly essential in the detoxification of superoxide free radicals in organisms that must deal with elemental oxygen.

• Synthesis of Amino Acids

  • For example, an aminoacylase enzyme from pig kidneys cleaves an amide derivative of a natural L-amino acid much faster than it does the D-enantiomer.
  • If the racemic mixture of amides shown in the green shaded box above is treated with this enzyme, the L-enantiomer (whatever its rotation) will be rapidly converted to its free zwitterionic form, whereas the D-enantiomer will remain largely unchanged.

• Transition State Theory

  • Transition state theory is most useful in the field of biochemistry, where it is often used to model reactions catalyzed by enzymes in the body.