Lyases;
Carbon-nitrogen lyases;
Ammonia-lyases
BRITE hierarchy

L-serine ammonia-lyase (pyruvate-forming)

L-serine = pyruvate + NH3 (overall reaction) [RN:R00220];
(1a) L-serine = 2-aminoprop-2-enoate + H2O [RN:R00590];
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous) [RN:R11100];
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous) [RN:R11099]

R00220 R00590 R11099 R11100;
(other) R06131
Reaction

L-serine [CPD:C00065];
2-aminoprop-2-enoate [CPD:C02218];
2-iminopropanoate [CPD:C20904];
H2O [CPD:C00001]

Most enzymes that catalyse this reaction are pyridoxal-phosphate-dependent, although some enzymes contain an iron-sulfur cluster instead [6]. The reaction catalysed by both types of enzymes involves the initial elimination of water to form an enamine intermediate (hence the enzyme's original classification as EC 4.2.1.13, L-serine dehydratase), followed by tautomerization to an imine form and hydrolysis of the C-N bond. The latter reaction, which can occur spontaneously, is also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase. This reaction is also carried out by EC 4.3.1.19, threonine ammonia-lyase, from a number of sources.

EC 4.3.1.17 created 1961 as EC 4.2.1.13, transferred 2001 to EC 4.3.1.17, modified 2014