Tryptophan synthase beta superfamily (fold type II); this family of pyridoxal phosphate (PLP)-dependent enzymes catalyzes beta-replacement and beta-elimination reactions. This CD corresponds to aminocyclopropane-1-carboxylate deaminase (ACCD), tryptophan synthase beta chain (Trp-synth_B), cystathionine beta-synthase (CBS), O-acetylserine sulfhydrylase (CS), serine dehydratase (Ser-dehyd), threonine dehydratase (Thr-dehyd), diaminopropionate ammonia lyase (DAL), and threonine synthase (Thr-synth). ACCD catalyzes the conversion of 1-aminocyclopropane-1-carboxylate to alpha-ketobutyrate and ammonia. Tryptophan synthase folds into a tetramer, where the beta chain is the catalytic PLP-binding subunit and catalyzes the formation of L-tryptophan from indole and L-serine. CBS is a tetrameric hemeprotein that catalyzes condensation of serine and homocysteine to cystathionine. CS is a homodimer that catalyzes the formation of L-cysteine from O-acetyl-L-serine. Ser-dehyd catalyzes the conversion of L- or D-serine to pyruvate and ammonia. Thr-dehyd is active as a homodimer and catalyzes the conversion of L-threonine to 2-oxobutanoate and ammonia. DAL is also a homodimer and catalyzes the alpha, beta-elimination reaction of both L- and D-alpha, beta-diaminopropionate to form pyruvate and ammonia. Thr-synth catalyzes the formation of threonine and inorganic phosphate from O-phosphohomoserine.