ID 4.2.1.22 DE cystathionine beta-synthase. AN beta-thionase. AN methylcysteine synthase. AN serine sulfhydrase. CA L-homocysteine + L-serine = H2O + L,L-cystathionine. CC -!- A multifunctional enzyme: catalyzes beta-replacement reaction between CC L-serine, L-cysteine, cysteine thioethers or some other beta- CC substituted alpha-L-amino acids and a variety of mercaptans. CC -!- Formerly EC 4.2.1.21. DR G5EFH8, CBS1_CAEEL ; Q9N4K2, CBS2_CAEEL ; Q2V0C9, CBS_APIME ; DR P46794, CBS_DICDI ; P35520, CBS_HUMAN ; Q58H57, CBS_MACFA ; DR Q91WT9, CBS_MOUSE ; Q9N0V7, CBS_RABIT ; P32232, CBS_RAT ; DR P32582, CBS_YEAST ; Q9YBL2, CYSO_AERPE ; P9WP50, Y1077_MYCTO; DR P9WP51, Y1077_MYCTU; //