IUBMB Enzymes

IUBMB: International Union of Biochemistry and Molecular Biology

国际生物化学与分子生物学联盟

Seems that KEGG now divides all the reactions stored in their BRITE database into six categories according to some IUBMB regulation. They are: Oxidoreductases reactions(氧化还原反应), Transferases reactions(转移酶反应), Hydrolases reactions(水解酶反应), Lyases reactions(裂合酶反应), Isomerases reactions(别构酶反应) and Ligases reactions(连接酶反应)。 Obviously they are categorized by the function of the involved enzymes.

From Wikipedia, we got the definition of the 6 types of enzymes:

Oxidoreductases(氧化还原酶)： In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule (the reductant, also called the hydrogen or electron donor) to another (the oxidant, also called the hydrogen or electron acceptor).

For example, an enzyme that catalyzed this reaction would be an oxidoreductase:

A^– + B → A + B^–

In this example, A is the reductant (electron donor) and B is the oxidant (electron acceptor).

In biochemical reactions, the redox reactions are sometimes more difficult to see, such as this reaction from glycolysis:

P_i + glyceraldehyde-3-phosphate + NAD⁺ → NADH + H⁺ + 1,3-bisphosphoglycerate

In this reaction, NAD⁺ is the oxidant (electron acceptor), and glyceraldehyde-3-phosphate is the reductant (electron donor).

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Transferases(转移酶)：In biochemistry, a transferase is an enzyme that catalyzes the transfer of a functional group (e.g. a methyl or phosphate group) from one molecule (called the donor) to another (called the acceptor). For example, an enzyme that catalyzed this reaction would be a transferase:

A–X + B → A + B–X

In this example, A would be the donor, and B would be the acceptor. The donor is often a coenzyme.

Hydrolases(水解酶)： In biochemistry, a hydrolase is an enzyme that catalyzes the hydrolysis of a chemical bond. For example, an enzyme that catalyzed the following reaction is a hydrolase:

A–B + H₂O → A–OH + B–H

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Lyase(裂合酶): 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.

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Isomerases(别构酶)：In biochemistry, an isomerase is an enzyme that catalyses the structural rearrangement of isomers. Isomerases thus catalyze reactions of the form A → B 。

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Ligase(连接酶): In biochemistry, a ligase (from the Latin verb ligāre — "to bind" or "to glue together") is an enzyme that can catalyse the joining of two large molecules by forming a new chemical bond, usually with accompanying hydrolysis of a small chemical group pendant to one of the larger molecules. Generally ligase catalyses the following reaction:

Ab + C → A–C + b

or sometimes

Ab + cD → A–D + b + c

where the lower case letters signify the small, pendant groups.