Active-site-directed irreversible inhibition of rat brain 4-aminobutyrate aminotransferase by ethanolamine O-sulphate in vitro and in vivo.
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ABSTRACT:
SUBMITTER: Fowler LJ
PROVIDER: S-EPMC1174437 | biostudies-other | 1972 Nov
REPOSITORIES: biostudies-other
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Project description: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.
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