Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB)

Enzyme Nomenclature. Recommendations

EC 4.3

Carbon-Nitrogen Lyases


EC 4.3.1 Ammonia-Lyases

EC 4.3.2 Lyases Acting on Amides, Amidines, etc.

EC 4.3.3 Amine-Lyases

EC 4.3.99 Other Carbon-Nitrogen Lyases

This subclass contains the enzymes that release ammonia or one of its derivatives, with the formation of a double bond or ring. Some catalyse the actual elimination of the ammonia, amine or amide, e.g.

>CH-CH(-NH-R)- → >C=CH- + NH2-R

Others, however, catalyse elimination of another component, e.g. water, which is followed by spontaneous reactions that lead to breakage of the C-N bond, e.g.

as in EC (L-serine ammonia-lyase), so that the overall reaction is

>C(-OH)-CH(-NH2)- → >CH2-CO- + NH3

i.e., an elimination with rearrangement.

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