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enzyme (lysozyme)

  Enzyme classes:
  EC 1: Oxidoreductases
  EC 2: Transferases
  EC 3: Hydrolases
  EC 4: Lyases
  EC 5: Isomerases
  EC 6: Ligases
  General information:
  Catalytic mechanism
  Enzyme kinetics
  Enzymes in industry


About Enzymes

Enzymes are proteins that increase the rates (catalyse) of chemical reactions. All chemical processes in living cells are carried out by enzymes. Enzymes are very specific and usually catalyse only one specific reaction. The set of enzymatic reactions by converting of substrate to the final products is metabolic pathway. Some metabolic pathways are duplicated by another sets of enzymes, but some of them are unique. Enzymes involved into pathways which are not duplicated in living cells and crucial for normal cell functioning are called "essential enzymes". Knowledges about essential enzymes are very important for understanding of biological cell functioning and for drug design and development.

According to Nucleic Acids Research in 2000 it was known about 4000 different reactions, catalyzed by enzymes. Like other catalysts, enzymes are lowering the activation energy of reaction to be catalyzed with subsequent acceleration of reaction up to millions of times. Enzymes are not alter the equilibrium of chemical reactions.

Understanding of mechanism and specificity of each particular enzyme allow to produce a very specific inhibitors, which will be able to significantly reduce or completely stop this enzyme. Such inhibitors are often used as a drugs or antibiotics against bacterial cells. Furthermore, many enzymes are used commercially.

EC classification of Enzymes and Nomenclature

This classification is based on recommendations of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB) on the Nomenclature and Classification of Enzymes by the Reactions they Catalyse

EC 1 Oxidoreductases - these enzymes catalyse oxido-reduction
EC 2 Transferases - these enzymes catalyse the transfer of a chemical group from donor to acceptor.
EC 3 Hydrolases - these enzymes catalyse the hydrolysis of various bonds.
EC 4 Lyases - these enzymes cleaving bonds by other means than by hydrolysis or oxidation.
EC 5 Isomerases - these enzymes catalyse changes within one molecule.
EC 6 Ligases - these enzymes catalyse the joining of two molecules with concomitant hydrolysis of the diphosphate bond in triphosphates.

Interesting enzymes

Here is the list of the most important and interesting enzymes.
  • Lysozyme - 129 aminoacid residues (Mr = 14.7 kDa) enzyme (EC which catalyse hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan and some other similar bonds. This enzyme is wide spread in living organisms and now this one of the best enzyme for many studies.
  • Amylase - Group of enzymes belonging to EC 3.2.1 group, which catalyse the hydrolysis of glycosides. Well known by reaction of hydrolysis of starch into maltose molecules. This enzyme was isolated in 1833 by Anselme Payen.
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