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Structure And Function Of Enzymes Essaytyper

GENERAL ASSEMBLY
Is where all partners  meet once a year (autumn). The Assembly debates and decides the overall programme of the network and the policy direction for the future, based on recommendations made by the Executive Council. The General Assembly also provides a forum for policy debate and establishes the basis for the definition of the network’s political agenda.

EXECUTIVE COUNCIL
It is the body competent to follow the work progress and ensure the implementation of all General Assembly decisions. The Executive Council is composed by 5 members of the Eurotowns Network and by the President and two vice Presidents. They  meet on trimestrial basis checks to discuss daily management of the network/ controll network priorities/ check on major relevant events/ promotes networking actions/ partnership enlargement.

TASK TEAM
Work is organised around task teams:

  • Carry out the work program of the network based on the key challenges as defined by the general Assembly or the Executive Council;
  • Work in a specific area or subject through confrontation / round tables / surveys and report progress to the Executive Council;
  • Evaluate the possibility of accessing external sources of finance for the work.

Task teams receive network funding in order to develop project ideas of to implement studies and researches, facilitate confrontation.

The Executive council (2016-2018) is composed by:

Presidency
Municipality of Sindelfingen (Germany)

Vice-presidency
Municipality of Reggio Emilia (Italy)
Municipality of Schiedam (Netherlands)

Executive Council Members
Municipality of Gävle (Sweden)
Municipality of Hasselt (Belgium)
Municipality of Hastings (United Kingdom)
Municipality of Sabadell (Spain)
Municipality of Varberg (Sweden)

Network main bodies rotate every 2 years and are elected by the General Assembly.

In this lesson, the three-dimensional structure of proteins will be discussed: the primary structure of polypeptides, secondary structures in proteins (α-helix, β-sheet), and the tertiary structure. The concept of an enzyme active site will be introduced.

Aims
By the end of this lesson, you should

  1. be familiar with the main features of protein structure
  2. understand the concept of an enzyme active site

What is an enzyme?[edit]

  • Enzymes are protein macromolecules.
    • They have a defined amino acid sequence, and are typically 100-500 amino acids long.
    • They have a defined three-dimensional structure.
  • Enzymes are catalysts.
    • They act as a catalyst to a chemical or biochemical reaction, with a defined mechanism.
    • They increase the speed of that reaction, typically by 106-1014 times faster than the rate of the uncatalysed reaction.
    • They are selective for a single substrate.
    • They speed up rate of reaction by lowering the activation energy (Ea).
    • They are stereospecific, meaning the reaction produces a single product.

Enzyme structure[edit]

Primary structure[edit]

Enzymes are made up of amino acids which are linked together via amide (peptide) bonds in a linear chain. This is the primary structure. The resulting amino acid chain is called a polypeptide or protein. The specific order of amino acids in the protein is encoded by the DNA sequence of the corresponding gene.

Click here for a list of all 21 amino acids.

Secondary structure[edit]

The hydrogen in the amino group (NH2) and the oxygen in the carboxyl group (COOH) of each amino acid can bond with each other by means of hydrogen bond, this means that the amino acids in the same chain can interact with each other. As a result, the protein chain can fold up on itself, and it can fold up in two ways, resulting in two secondary structures: it can either wrap round forming the α-helix, or it can fold on top of itself forming the β-sheet.

  • Molecular diagram of β-sheets

In the images above, the dotted lines represent the hydrogen bonds. There are two forms of β-sheet, depending on the direction of the protein chain. If the direction alternates between every fold, it forms an anti-parallel sheet; if it remains the same direction, it forms a parallel sheet.

Tertiary structure[edit]

As a consequence of the folding-up of the 2D linear chain in the secondary structure, the protein can fold up further and in doing so gains a three-dimensional structure. This is its tertiary structure.

Substrate binding[edit]

All enzymes have an active site, where the reaction is catalysed. This part of the enzyme has the specific shape and functional groups to bind to the reacting molecules (called the substrate). Hence the active site contains a small number of catalytic amino acids, which are essential in catalysing the reaction. The substrate molecule can bind to the active site via non-covalent interactions:

  1. electrostatic interactions
    for example, those amino acids in section A of this list will attract an oppositely charged substrate.
  2. hydrogen bonding
    typically between the amide and carboxyl groups of the amino acid can hydrogen bonds form with the substrate.
  3. Van der Waals interactions
    for example, those amino acids in section B of this list.
  4. hydrophobic interactions
    for example, those amino acids in section D of this list will repel water.


Next lesson: Enzyme catalysis

α-chymotrypsin. The labelled amino acids form the active site of the enzyme.
Lysozyme. The red helices are α-helices, and the blue arrows the β-sheets.

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