enzymes

Examples of enzymes in the following topics:

• Enzymes Used in Industry

  • Synthetic molecules, called artificial enzymes, also display enzyme-like catalysis.
  • Inhibitors can decrease enzyme activity; activators can increase activity.
  • Many drugs and poisons are enzyme inhibitors.
  • In addition, some household products use enzymes to speed up biochemical reactions (e.g., enzymes in biological washing powders break down protein or fat stains on clothes; enzymes in meat tenderizers break down proteins into smaller molecules, making the meat easier to chew).
  • Industrially-produced barley enzymes are widely used in the brewing process to substitute for the natural enzymes found in barley.

• Molecular Products from Microbes

  • Taq polymerase is an enzyme that was first isolated from the microbe Thermus aquaticus.
  • Restriction enzymes are a specific class of enzymes isolated from various bacteria and archaea, in which they grow naturally as a means of protection against viral infection.
  • The enzymes have the ability to recognize foreign DNA and cut it up.
  • The bacteria and archaea from which these enzymes are isolated from have innate mechanisms to protect their own DNA sequences from these enzymes, such as methylation.
  • Describe how Taq polymerase, restriction enzymes and DNA ligase are used in molecular biology

• Carboxysomes

  • Carboxysomes are intracellular structures that contain enzymes involved in carbon fixation and found in many autotrophic bacteria.
  • They are proteinaceous structures resembling phage heads in their morphology; they contain the enzymes of carbon dioxide fixation in these organisms.
  • Similar structures are known to harbor the B12-containing coenzyme glycerol dehydratase, the key enzyme of glycerol fermentation to 1,3-propanediol, in some Enterobacteriaceae, such as Salmonella.
  • Carboxysomes are bacterial microcompartments that contain enzymes involved in carbon fixation.
  • These compartments are thought to concentrate carbon dioxide to overcome the inefficiency of RuBisCo (ribulose bisphosphate carboxylase/oxygenase) - the predominant enzyme in carbon fixation and the rate limiting enzyme in the Calvin cycle.

• Protease Inhibitors

  • Protease inhibitors target viral proteases which are key enzymes for the completion of viral maturation.
  • Proteases are enzymes that have the ability to cut proteins into peptides.
  • Protease inhibitors are short peptide-like molecules that are competitive inhibitors of the enzyme.
  • Mutations in the enzyme active site and other sites, which cause conformational changes, can cause resistance.
  • The drug is ritonavir depicted here with a white molecule in the middle of the enzyme structure.

• Inhibiting Nucleic Acid Synthesis

  • Antimicrobial drugs inhibit nucleic acid synthesis through differences in prokaryotic and eukaryotic enzymes.
  • The antimicrobial actions of these agents are a result of differences in prokaryotic and eukaryotic enzymes involved in nucleic acid synthesis.
  • RNA Polymerase, an enzyme that produces RNA, from T. aquaticus pictured during elongation.
  • Portions of the enzyme were made transparent so as to make the path of RNA and DNA more clear.
  • The magnesium ion (yellow) is located at the enzyme active site.

• Enzyme-Linked Immunosorbent Assay (ELISA)

  • Enzyme-linked immunosorbent assay (ELISA) is a solid-phase enzyme immunoassay used to detect the presence of a substance in solution.
  • ELISA uses a specific antibody with a covalently coupled enzyme.
  • Unbound antigen is removed by washing, and a second antibody which is linked to an enzyme is allowed to bind.
  • This second antibody-enzyme complex constitutes the indicator system of the test.
  • The antigen serves as bridge, so the more antigen in the test solution, the more enzyme-linked antibody will bind .

• Nucleotide and Nonnucleotide Reverse Transcriptase Inhibitors

  • Reverse transcriptase is an enzyme that has the ability to transcribe single-stranded DNA from a single-stranded RNA chain.
  • This enzyme is also found in tumors and cancer cells.
  • Drugs that inhibit the function of this enzyme are divided into three groups:
  • Resistance to the non-nucleotide inhibitors is caused by mutations in the inhibitor binding site of the enzyme.
  • Such mutations prevent the binding of the inhibitor to the enzyme.

• Regulation of the Calvin Cycle

  • Each of these phases are tightly regulated and require unique and specific enzymes.
  • RuBisCO is identified as the most abundant enzyme on earth, to date.
  • The enzyme aldolase is typically characterized as a glycolytic enzyme with the ability to split fructose 1,6-bisphosphate into DHAP and G3P.
  • This process requires ATP and specific enzymes.
  • After this final enzyme performs this conversion, the Calvin cycle is considered complete.

• Cofactors and Energy Transitions

  • These proteins are commonly enzymes.
  • An inactive enzyme without the cofactor is called an apoenzyme, while the complete enzyme with cofactor is the holoenzyme.
  • Some enzymes or enzyme complexes require several cofactors.
  • Each class of group-transfer reaction is carried out by a particular cofactor, which is the substrate for a set of enzymes that produce it and a set of enzymes that consume it.
  • Here, hundreds of separate types of enzymes remove electrons from their substrates and reduce NAD+ to NADH.

• Oxidoreductase Protein Complexes

  • In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule to another.
  • In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another the oxidant, also called the electron acceptor.
  • This group of enzymes usually utilizes NADP or NAD+ as cofactors.
  • For example, an enzyme that catalyzed this reaction would be an oxidoreductase: A– + B → A + B–.
  • Oxidoreductases are classified as EC 1 in the EC number classification of enzymes.