title: Inactivation of ethanolamine ammonia-lyase by 5,5'-dithiobis(2-nitrobenzoic acid). Further evidence for the involvement of sulfhydryl groups in adenosylcobalamin-dependent rearrangements.
abstract: Treatment of the adenosylcobalamin-requiring enzyme ethanolamine ammonia-lyase (EC 4.3.1.7) with 5,5'-dithiobis(2-nitrobenzoic acid) (Nbs2) discloses three classes of -SH groups: a rapidly reacting class (2 -SH groups/enzyme molecule), a slowly reacting class (6 -SH groups/molecule) and a class which does not react unless the enzyme is denatured (7 -SH groups/molecule (Kaplan, B.H. and Stadtman, E.R. (1968) J. Biol. Chem. 243, 1794)). The enzyme is inactivated by Nbs2 at a rate similar to the rate at which Nbs2 reacts with the slowly reacting class of -SH groups. Inactivation of the enzyme is retarded by adenosylcobalamin but not by ethanolamine. Once inactivated, the enzyme cannot be reactivated with mercaptoethanol. These observations provide further evidence for the importance of -SH groups in catalysis by adenosyl-cobalamin-requiring enzymes.
mesh_terms: D000642:Ammonia-Lyases / Q000037:antagonists & inhibitors*; D003013:Clostridium / Q000201:enzymology; D003038:Cobamides / Q000494:pharmacology*; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology*; D004981:Ethanolamine Ammonia-Lyase / Q000037:antagonists & inhibitors*; D004983:Ethanolamines / Q000494:pharmacology; D007700:Kinetics; D008623:Mercaptoethanol / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000378:metabolism*
chemical_list: D003038:Cobamides; D004983:Ethanolamines; D009579:Nitrobenzoates; D013438:Sulfhydryl Compounds; D008623:Mercaptoethanol; D004228:Dithionitrobenzoic Acid; D000642:Ammonia-Lyases; D004981:Ethanolamine Ammonia-Lyase