EnzymeDSDbase is a database on disulphide bonds in enzymes that provides information on native disulphides and those which are stereochemically possible between pairs of residues in an enzyme.This database currently contains 9313 enzyme entries(as at 31 July 2002).The enzymes are classified by their E.C. number as found in the Enzyme Structures Database.

E.C.1   OXIDOREDUCTASES.

The oxidoreductases catalyse oxido-reductions. The substrate oxidised is regarded as an hydrogen or electron donor.

The E.C. classification for these enzymes classifies them firstly by the donor group that undergoes oxidation, then by the acceptor, and lastly by the enzyme.

The recommended name for these enzymes is dehydrogenase. An alternative name is reductase. The name oxidase is only used where O(2) is the acceptor.
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E.C.2   TRANSFERASES.

Transferases are enzymes that transfer a group (eg a methyl or glycosyl group) from one compound (which is generally regarded as the donor) to another compound (generally regarded as the acceptor).

The E.C. classification for these enzymes classifies them firstly by the donor group, then by the acceptor, and lastly by the enzyme.

The recommended names are normally formed as: acceptor-group transferase, or donor-group transferase. in many cases the donor is a cofactor (coenzyme) charged with the group to be transferred.
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E.C.3   HYDROLASES.

The hydrolases catalyse the hydrolytic cleavage of C-O, C-N, C-C and some other bonds, including phosphoric anhydride bonds.

The E.C. classification for these enzymes generally classifies them firstly by the nature of the bond hydrolysed, then by the nature of the substrate, and lastly by the enzyme.

Although the systematic name always includes hydrolase, the recommended name is, in many cases, formed by the name of the substrate with the suffix -ase. It is understood that the name of the substrate with this suffix means a hydrolytic enzyme.
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E.C.4   LYASES.

The lyases are enzymes cleaving C-C, C-O, C-N, and other bonds by elimination, leaving double bonds or rings, or conversely adding groups to double bonds.
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E.C.5   ISOMERASES.

The isomerases catalyse geometric or structural changes within one molecule.

According to the type of isomerism, they may be called racemases, epimerases, cis-tran-isomerases, isomerases, tautomerases, mutases or cylcoisomerases.

The subclasses are defined according to the type of isomerism, the sub-subclasses to the type of substrates.
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E.C.6   LIGASES.

The ligases catalyse the joining together of two molecules coupled with the hydrolysis of a pyrophosphate bond in ATP or a similar triphosphate. The bonds formed are often high-energy bonds.

The subclasses are defined according to the type of bond formed; the sub-subclasses are only used in the C-N ligases.
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