Cysteine synthase A; Belongs to the cysteine synthase/cystathionine beta- synthase family.

Pyridoxal-phosphate dependent enzyme.

Cysteine synthase A.

cysteinyl-tRNA synthetase; Belongs to the class-I aminoacyl-tRNA synthetase family.

Serine O-acetyltransferase.

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.

Threonine dehydratase; 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.

Homoserine kinase; Catalyzes the ATP-dependent phosphorylation of L-homoserine to L-homoserine phosphate; Belongs to the GHMP kinase family. Homoserine kinase subfamily.