Characteristic Features of Kynurenine Aminotransferase Allosterically Regulated by Alpha-Ketoglutarate in Cooperation with KynurenineReportar como inadecuado




Characteristic Features of Kynurenine Aminotransferase Allosterically Regulated by Alpha-Ketoglutarate in Cooperation with Kynurenine - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Kynurenine aminotransferase from Pyrococcus horikoshii OT3 PhKAT, which is a homodimeric protein, catalyzes the conversion of kynurenine KYN to kynurenic acid KYNA. We analyzed the transaminase reaction mechanisms of this protein with pyridoxal-5′-phosphate PLP, KYN and α-ketoglutaric acid 2OG or oxaloacetic acid OXA. 2OG significantly inhibited KAT activities in kinetic analyses, suggesting that a KYNA biosynthesis is allosterically regulated by 2OG. Its inhibitions evidently were unlocked by KYN. 2OG and KYN functioned as an inhibitor and activator in response to changes in the concentrations of KYN and 2OG, respectively. The affinities of one subunit for PLP or 2OG were different from that of the other subunit, as confirmed by spectrophotometry and isothermal titration calorimetry, suggesting that the difference of affinities between subunits might play a role in regulations of the KAT reaction. Moreover, we identified two active and allosteric sites in the crystal structure of PhKAT-2OG complexes. The crystal structure of PhKAT in complex with four 2OGs demonstrates that two 2OGs in allosteric sites are effector molecules which inhibit the KYNA productions. Thus, the combined data lead to the conclusion that PhKAT probably is regulated by allosteric control machineries, with 2OG as the allosteric inhibitor.



Autor: Ken Okada , Clement Angkawidjaja, Yuichi Koga, Kazufumi Takano, Shigenori Kanaya

Fuente: http://plos.srce.hr/



DESCARGAR PDF




Documentos relacionados