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Results for “Ketoglutaric Acids”

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At least 19 recordsLinked to original sources
PubMed1977

Mechanism of the irreversible inhibition of gamma-aminobutyric acid-alpha-ketoglutaric acid transaminase by the neutrotoxin gabaculine.

Gabaculine (5-amino-1,3-cyclohexadienylcarboxylic acid), a naturally occurring amino acid isolated from Streptomyces toyacaenis, is an irreversible inhibitor of bacterial pyridoxal phosphate linked gamma-aminobutyric acid-alpha-ketoglutaric acid transaminase with a t 1/2 (25 degrees C) of 9 min at 3 X 10(-7) M. Gabaculine is a substrate for gamma-aminobutyric acid transaminase. The measured KI is 2.86 X 10(-6) M, and the kcat for its turnover is 1.15 X 10(-2) S-1 at 25 degrees C. When gabaculine is transaminated by the enzyme, it is converted to a cyclohexatrienyl system with one exo double bond. Upon spontaneous aromatization, this high energy intermediate is transformed into a stable m-anthranilic acid derivative (m-carboxyphenylpyridoxamine phosphate), which results in the covalent and irreversible modification of the cofactor. This adduct is bound tightly to the active site of the enzyme and can be liberated under denaturing conditions.

4-Aminobutyrate Transaminase↗
PubMed1981

Mechanism of inactivation of gamma-aminobutyric acid-alpha-ketoglutaric acid aminotransferase by 4-amino-5-halopentanoic acids.

(S)-4-Amino-5-halopentanoic acids were previously shown to irreversibly inhibit pig brain gamma-aminobutyric acid--alpha-ketoglutaric acid aminotransferase, and a mechanism for the inactivation was proposed (Silverman, R. B., & Levy M. A. (1980) Biochem. Biophys. Res. Commun. 95, 250). Evidence is presented to show that these compounds are mechanism-based inactivators, and experiments are described to elucidate their mechanism of action. The enzyme must be in the pyridoxal phosphate form for inactivation to occur, the gamma proton of the inactivators is removed in a rate-determining step, and one fluoride ion is released from 4-amino-5-fluoropentanoic acid per active site labeled. The change in the optical spectrum of the enzyme during inactivation suggests that the coenzyme is converted into the pyridoxamine phosphate form. Every turnover of inactivator leads to an inactivation event, i.e., the partition ratio is zero.

4-Aminobutyrate Transaminase↗