Serine hydroxymethyltransferase; Catalyzes the reversible interconversion of serine and glycine with tetrahydrofolate (THF) serving as the one-carbon carrier. This reaction serves as the major source of one-carbon groups required for the biosynthesis of purines, thymidylate, methionine, and other important biomolecules. Also exhibits THF-independent aldolase activity toward beta-hydroxyamino acids, producing glycine and aldehydes, via a retro-aldol mechanism.

Tryptophan synthase, beta subunit; The beta subunit is responsible for the synthesis of L- tryptophan from indole and L-serine.

L-serine deaminase I; Belongs to the iron-sulfur dependent L-serine dehydratase family.

Threonine deaminase; Catalyzes the anaerobic formation of alpha-ketobutyrate and ammonia from threonine in a two-step reaction. The first step involved a dehydration of threonine and a production of enamine intermediates (aminocrotonate), which tautomerizes to its imine form (iminobutyrate). Both intermediates are unstable and short-lived. The second step is the nonenzymatic hydrolysis of the enamine/imine intermediates to form 2- ketobutyrate and free ammonia. In the low water environment of the cell, the second step is accelerated by RidA.

Tryptophan synthase, alpha subunit; The alpha subunit is responsible for the aldol cleavage of indoleglycerol phosphate to indole and glyceraldehyde 3-phosphate. Belongs to the TrpA family.

Phosphatidylserine synthase; Belongs to the CDP-alcohol phosphatidyltransferase class-I family.

Serine acetyltransferase (SAT).

Homoserine O-acetyltransferase; Transfers a succinyl group from succinyl-CoA to L-homoserine, forming succinyl-L-homoserine.

Cysteine synthase; Catalyzes the synthesis of N-((2S)-2-amino-2-carboxyethyl)-L- glutamate (ACEGA) from O-phospho-L-serine and L-glutamate.