Lyase

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In biochemistry, a lyase is an enzyme that catalyzes the breaking of various chemical bonds by means other than hydrolysis and oxidation, often forming a new double bond or a new ring structure. For example, an enzyme that catalyzed this reaction would be a lyase:

ATP → cAMP + PP_i

Lyases differ from other enzymes in that they only require one substrate for the reaction in one direction, but two substrates for the reverse reaction.

Contents 1 Nomenclature 2 Classification 3 See also 4 References

[edit] Nomenclature

Systematic names are formed as "substrate group lyase." Common names include decarboxylase, dehydratase, aldolase, etc. When the reverse reaction is more important, synthase may be used in the name.

[edit] Classification

Lysases are classified as EC 4 in the EC number classification of enzymes. Lyases can be further classified into seven subclasses:

• EC 4.1 includes lyases that cleave carbon-carbon bonds, such as decarboxylases (EC 4.1.1), aldehyde lyases (EC 4.1.2), oxo acid lyases(EC 4.1.3) and others (EC 4.1.99)
• EC 4.2 includes lyases that cleave carbon-oxygen bonds, such as dehydratases
• EC 4.3 includes lyases that cleave carbon-nitrogen bonds
• EC 4.4 includes lyases that cleave carbon-sulfur bonds
• EC 4.5 includes lyases that cleave carbon-halide bonds
• EC 4.6 includes lyases that cleave phosphorus-oxygen bonds, such as adenylate cyclase and guanylate cyclase
• EC 4.99 includes other lyases, such as ferrochelatase

[edit] See also

• List of EC numbers of enzymes belonging to category EC 4

[edit] References

• EC 4 Introduction from the Department of Chemistry at Queen Mary, University of London

v • d • e Proteins: enzymes Topics Active site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number Enzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes Types EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list

v • d • e Carbon-carbon lyases (EC 4.1) 4.1.1: Carboxy-lyases Pyruvate decarboxylase -Oxaloacetate decarboxylase - Acetoacetate decarboxylase - Malonyl-CoA decarboxylase - Glutamate decarboxylase - Ornithine decarboxylase - Lysine decarboxylase - Phosphoribosylaminoimidazole carboxylase - Histidine decarboxylase - Uridine monophosphate synthetase/Orotidine 5'-phosphate decarboxylase - Aromatic L-amino acid decarboxylase - Phosphoenolpyruvate carboxylase - Pyrophosphomevalonate decarboxylase - Uroporphyrinogen III decarboxylase - RuBisCO - Phosphoenolpyruvate carboxykinase - Adenosylmethionine decarboxylase 4.1.2: Aldehyde-lyases Aldolase A/Aldolase B - 2-hydroxyphytanoyl-CoA lyase - Threonine aldolase 4.1.3: Oxo-acid-lyases 3-hydroxy-3-methylglutaryl-CoA lyase

v • d • e Carbon-oxygen lyases (EC 4.2) (primarily dehydratases) Carbonic anhydrase - Fumarase - Aconitase - Enolase (Alpha) - Enoyl-CoA hydratase/3-Hydroxyacyl ACP dehydrase - Methylglutaconyl-CoA hydratase - Tryptophan synthase - Cystathionine beta synthase - Porphobilinogen synthase - 3-isopropylmalate dehydratase - Urocanate hydratase - Uroporphyrinogen III synthase - Nitrile hydratase

v • d • e Carbon-nitrogen lyases (EC 4.3) 4.3.1 - ammonia-lyases Histidine ammonia-lyase - Formiminotransferase cyclodeaminase - Serine dehydratase 4.3.2 - amidine-lyases Argininosuccinate lyase - Adenylosuccinate lyase

v • d • e Carbon-sulfur lyases (EC 4.4) Cystathionine gamma-lyase - Cystathionine-beta-lyase - Leukotriene C4 synthase

v • d • e Carbon-halide lyases (EC 4.5) Dichloromethane dehalogenase - Halohydrin dehalogenase

v • d • e Phosphorus-oxygen lyases (EC 4.6) Adenylate cyclase - Guanylate cyclase (2D, c)