biochemistry Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, a ...

, a lyase is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that catalyzes the breaking (an

elimination reaction An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 r ...

) of various

chemical bond A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons a ...

s by means other than

hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

substitution reaction A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. Substitution reactions ar ...

) and

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

, often forming a new

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

or a new ring structure. The reverse reaction is also possible (called a Michael reaction). For example, an enzyme that catalyzed this reaction would be a lyase: : ATP → cAMP + PP_i Lyases differ from other enzymes in that they require only one

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...

for the reaction in one direction, but two substrates for the reverse reaction.

Nomenclature

Systematic names are formed as "''substrate group-lyase''." Common names include

decarboxylase Carboxy-lyases, also known as decarboxylases, are carbon–carbon lyases that add or remove a carboxyl group from organic compounds. These enzymes catalyze the decarboxylation of amino acids and alpha-keto acids. Classification and nomenclature ...

, dehydratase,

aldolase Fructose-bisphosphate aldolase (), often just aldolase, is an enzyme catalyzing a reversible reaction that splits the aldol, fructose 1,6-bisphosphate, into the triose phosphates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphat ...

, etc. When the product is more important, synthase may be used in the name, e.g. phosphosulfolactate synthase (EC 4.4.1.19, Michael addition of sulfite to phosphoenolpyruvate). A combination of both an elimination and a Michael addition is seen in O-succinylhomoserine (thiol)-lyase (MetY or MetZ) which catalyses first the γ-elimination of O-succinylhomoserine (with succinate as a leaving group) and then the addition of sulfide to the vinyl intermediate, this reaction was first classified as a lyase (EC 4.2.99.9), but was then reclassified as a transferase (EC 2.5.1.48).

Classification

Lyases 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

s (EC 4.1.1),

aldehyde lyases Fructose-bisphosphate aldolase (), often just aldolase, is an enzyme catalyzing a reversible reaction that splits the aldol, fructose 1,6-bisphosphate, into the triose phosphates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate ( ...

(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

adenylyl cyclase Adenylate cyclase (EC 4.6.1.1, also commonly known as adenyl cyclase and adenylyl cyclase, abbreviated AC) is an enzyme with systematic name ATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming). It catalyzes the following reaction: :A ...

and

guanylyl cyclase Guanosine monophosphate (GMP), also known as 5′-guanidylic acid or guanylic acid ( conjugate base guanylate), is a nucleotide that is used as a monomer in RNA. It is an ester of phosphoric acid with the nucleoside guanosine. GMP consists of th ...

* EC 4.99 includes other lyases, such as ferrochelatase

Membrane-associated lyases

Some lyases associate with biological membranes as

peripheral membrane protein Peripheral membrane proteins, or extrinsic membrane proteins, are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the periph ...

s or anchored through a single transmembrane helix.Superfamilies of single-pass transmembrane lyases
in Membranome database

References

EC 4 Introduction
from the Department of Chemistry at

Queen Mary, University of London Queen Mary University of London (QMUL, or informally QM, and formerly Queen Mary and Westfield College) is a public research university in Mile End, East London, England. It is a member institution of the federal University of London. Today, ...

{{enzyme-stub

Nomenclature

Classification

Membrane-associated lyases

See also

References