The effect of carboxylates and halides on L-lysine 6-aminotransferase-catalyzed reactions.
L-Lysine:2-oxoglutarate 6-aminotransferase catalyzes very slow transamination between L-alanine and 2-oxoglutarate. A high concentration of anions such as formate, acetate and halides greatly accelerated this transamination without affecting the affinity of the enzyme for L-alanine. In contrast, the anions strongly inhibited the normal L-lysine 6-transamination in a competitive manner with L-lysine and in a non-competitive manner with 2-oxoglutarate. This result suggests that the enzyme has an anion binding site which normally binds the carboxyl group of L-lysine. The binding of halides or carboxylates to this site probably induces a conformational change of the enzyme, and results in the inhibition of L-lysine 6-transamination, and in the stimulation of L-alanine transamination. Treatment of the enzyme with an arginine-specific dicarbonyl reagent, phenylglyoxal, led to a loss of the enzyme activity for L-lysine. The activity for L-alanine was not affected, but the stimulating effect of anions on L-alanine transamination was impaired. Thus, it is suggested that an arginine residue(s) plays an important role in the anion binding site.
D000409:Alanine / Q000378:metabolism; D002264:Carboxylic Acids / Q000494:pharmacology*; D055598:Chemical Phenomena; D002621:Chemistry; D002712:Chlorides / Q000494:pharmacology; D005561:Formates / Q000494:pharmacology; D006219:Halogens / Q000494:pharmacology*; D007700:Kinetics; D051306:L-Lysine 6-Transaminase; D008239:Lysine / Q000378:metabolism; D010658:Phenylglyoxal / Q000494:pharmacology; D000637:Transaminases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D002264:Carboxylic Acids; D002712:Chlorides; D005561:Formates; D006219:Halogens; D000637:Transaminases; D051306:L-Lysine 6-Transaminase; D008239:Lysine; D010658:Phenylglyoxal; D000409:Alanine