The reaction of ethanolamine O-sulphate with 4-aminobutyrate aminotransferase.
The enzyme-induced or 'suicide' step by which the substrate analogue ethanolamine O-sulphate inactivates 4-aminobutyrate aminotransferase occurs at a rate that is one-tenth that observed for the release of the products of beta-elimination, namely ammonia, acetaldehyde and sulphate. An additional reversible reaction not leading to inactivation can be detected spectrally and this decreases the rates of both beta-elimination and inactivation. This reaction is ascribed to a step on the normal transamination path, although complete transamination does not occur significantly. The 14C moiety of radiolabelled ethanolamine O-sulphate is stably bound to the inactive enzyme in the proportion of 1 mol/mol of active site. The 35S-labelled sulphate moiety is not bound after inactivation, showing that beta-elimination must precede inactivation.
D000612:4-Aminobutyrate Transaminase / Q000037:antagonists & inhibitors*; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000201:enzymology; D002250:Carbon Radioisotopes; D004789:Enzyme Activation / Q000187:drug effects; D004983:Ethanolamines / Q000494:pharmacology*; D007700:Kinetics; D011817:Rabbits; D013053:Spectrophotometry; D013462:Sulfur Radioisotopes; D000637:Transaminases / Q000037:antagonists & inhibitors*
D002250:Carbon Radioisotopes; D004983:Ethanolamines; D013462:Sulfur Radioisotopes; D000641:Ammonia; C020619:ethanolamine O-sulfate; D000637:Transaminases; D000612:4-Aminobutyrate Transaminase