RESUMO
The phosphinic analogues of tyrosine and pyruvate were first demonstrated to be substrates in the reactions of elimination and synthesis catalyzed by tyrosine phenol-lyase. Kinetic parameters of the enzymatic process were determined, and the first enzymic synthesis of an aminophosphinic acid was carried out. Replacement of the planar HOOC-group by the tetrahedral (HO)(O)PH-group in the substrate slightly affected its affinity for the enzyme but substantially diminished the conversion rate. For phosphonic analogues, containing (HO)2(O)P group, the affinity to the enzyme was decreased considerably while the conversion was completely prevented. Thus, the structural parameters of the acid group are important not only for the affinity for the enzyme, but also for the formation of the catalytically competent conformation of the active site.
Assuntos
Aminoácidos/metabolismo , Tirosina Fenol-Liase/metabolismo , Sítios de Ligação , Catálise , Citrobacter/enzimologia , Cinética , Modelos Químicos , Organofosfonatos/síntese química , Ligação Proteica , Ácido Pirúvico/metabolismo , Especificidade por Substrato , Tirosina/metabolismoRESUMO
Effects of a set of alpha-ketoglutarate phosphoanalogues on the activity of alpha-ketoglutarate dehydrogenase (EC 1.2.4.2) complexes from E. coli and pigeon breast muscle, as well as on alpha-ketoglutarate dehydrogenase isolated from the pigeon breast muscle, have been studied. alpha-Ketoglutarate phosphoanalogues (succinyl phosphonate and its monomethyl ester) were found to be effective inhibitors of alpha-ketoglutarate oxidative decarboxylation, catalyzed by both muscle and bacterial alpha-ketoglutarate dehydrogenase complexes, as well as muscle alpha-ketoglutarate dehydrogenase. The ability of glutamate phosphoanalogues to inhibit alpha-ketoglutarate oxidative decarboxylation has been shown in E. coli extract and a model system.
