Enzyme  Nomenclature  

Each enzyme is assigned two names. The first is its short, recommended name, convenient for everyday use. The second is the more complete systematic name, which is used when an enzyme must be identified without ambiguity.
A. Recommended name
Most commonly used enzyme names have the suffix “-ase” attached to the substrate of the reaction (for example, glucosidase and urease) or to a description of the action performed (for example, lactate dehydrogenase and adenylyl cyclase). [Note: Some enzymes retain their original trivial names, which give no hint of the associated enzymic reaction, for example, trypsin and pepsin.]
B. Systematic name
In the systematic naming system, enzymes are divided into six major classes (Fig. 1), each with numerous subgroups. For a given enzyme, the suffix - ase is attached to a fairly complete description of the chemical reaction catalyzed, including the names of all the substrates, for example, lactate:nicotinamide adenine dinucleotide (NAD+) oxidoreductase. [Note: Each enzyme is also assigned a classification number. Lactate:NAD+ oxidoreductase is 1.1.1.27.] The systematic names are unambiguous and
informative but are frequently too cumbersome to be of general use.

Figure 1:  The six major classes of enzymes with examples. NAD(H) =nicotinamide adenine dinucleotide; THF = tetrahydrofolate; CoA = coenzyme A; CO2 = carbon dioxide; NH3 = ammonia; ADP = adenosine diphosphate; Pi = inorganic phosphate.

Potentially confusing enzyme nomenclature includes synthetase (requires ATP), synthase (no ATP required), phosphatase (uses water to remove a phosphate group), phosphorylase (uses inorganic phosphate to break a bond and generate a phosphorylated product), dehydrogenase (NAD+ or flavin adenine dinucleotide [FAD] is an electron acceptor in a redox reaction), oxidase (oxygen is the acceptor, and oxygen atoms are not incorporated into substrate), and oxygenase (one or both oxygen atoms are incorporated).