Kynurenine aminotransferases in the rat. Localization and characterization.
Kynurenine-2-oxoglutarate aminotransferase (kynurenine specific, designated here KAT-II) and kynurenine pyruvate aminotransferase (designated here KAT-I) activities were detected in the kidney using 2 microM kynurenine. The major activities were performed by KAT-II and the contributi-n of KAT-I is about 1/15. KAT-I activity was detected in all organs tested. The liver showed the highest KAT-I activity, however, the highest activity of glutamine transaminase-K (GTK) was detected in the kidney. KAT-I activity was well corresponded with GTK activity in all organs except liver. KAT-I or GTK activity of crude extract didn't inhibited by addition of glutamine either kynurenine. KAT-I or GTK activity of purified preparation, however, inhibited strongly addition of glutamine either kynurenine. KAT-I and GTK showed different pH optimum profile, but purified and crude preparation of those were similar. Phenylpyruvate or 2-oxo-4-methiolbutyrate reduced the inhibition of purified KAT-I activity by glutamine using 2 microM kynurenine. Phenylpyruvate changed the Km value for kynurenine and Vmax, suggesting conformational change of the enzyme.
Okuno
E
E
Wakayayama Medical College, Wakayama, Japan.
Nishikawa
T
T
Nakamura
M
M
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D002852:Chromatography, Ion Exchange; D005973:Glutamine / Q000494:pharmacology; D007651:Keto Acids / Q000494:pharmacology; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D007737:Kynurenine / Q000031:analogs & derivatives / Q000494:pharmacology; D008190:Lyases; D008297:Male; D009928:Organ Specificity; D051381:Rats; D017207:Rats, Sprague-Dawley; D000637:Transaminases / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*
D000596:Amino Acids; D007651:Keto Acids; D005973:Glutamine; C005045:3-hydroxykynurenine; D007737:Kynurenine; D000637:Transaminases; C020656:glutamine-pyruvate aminotransferase; C427605:glutamine - phenylpyruvate transaminase; C021481:kynurenine-oxoglutarate transaminase; D008190:Lyases