Metabolism of β-valine via a CoA-dependent ammonia lyase pathway

摘要: Pseudomonas species strain SBV1 can rapidly grow on medium containing β-valine as a sole nitrogen source. The tertiary amine feature of prevents direct deamination reactions catalyzed by aminotransferases, amino acid dehydrogenases, and oxidases. However, lyase- or aminomutase-mediated conversions would be possible. To identify enzymes involved in the degradation β-valine, PsSBV1 gene library was prepared used to complement growth deficiency closely related strain. This resulted identification encoding β-valinyl-coenzyme A ligase (BvaA) two genes β-valinyl-CoA ammonia lyases (BvaB1 BvaB2). BvaA protein demonstrated high sequence identity several known phenylacetate CoA ligases. Purified enzyme did not convert phenyl acetic but able activate an adenosine triphosphate (ATP)- CoA-dependent manner. substrate range appears narrow, converting only lesser extent, 3-aminobutyrate β-alanine. Characterization BvaB1 BvaB2 revealed that both were deaminate produce 3-methylcrotonyl-CoA, common intermediate leucine pathway. Interestingly, no significant lyases, suggesting they belong new family enzymes. BLAST searches show each other enoyl-CoA hydratases, class catalyze similar reaction with water instead leaving group.