Members of this family are all pyridoxal-phosphate dependent enzymes. This family includes: serine dehydratase EC:4.2.1.13 P20132, threonine dehydratase EC:4.2.1.16 Swiss:P04968, tryptophan synthase beta chain EC:4.2.1.20 Swiss:P00932, threonine synthase EC:4.2.99.2 Swiss:P04990, cysteine synthase EC:4.2.99.8 P11096, cystathionine beta-synthase EC:4.2.1.22 Swiss:P35520, 1-aminocyclopropane-1-carboxylate deaminase EC:4.1.99.4 Swiss:P76316.