Glycine 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.

Threonine ammonia-lyase, biosynthetic; 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, beta subunit; The beta subunit is responsible for the synthesis of L- tryptophan from indole and L-serine.

L-serine ammonia-lyase; Belongs to the iron-sulfur dependent L-serine dehydratase family.

CDP-diacylglycerol--serine O-phosphatidyltransferase; Belongs to the CDP-alcohol phosphatidyltransferase class-I family.

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.

Serine O-acetyltransferase.

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

Imidazoleglycerol phosphate synthase, cyclase subunit; IGPS catalyzes the conversion of PRFAR and glutamine to IGP, AICAR and glutamate. The HisF subunit catalyzes the cyclization activity that produces IGP and AICAR from PRFAR using the ammonia provided by the HisH subunit.