Metabolism of amino acid amides in Pseudomonas putida ATCC 12633

Abstract

The metabolism of the natural amino acid l-valine, the unnatural amino acids d-valine, and d-, l-phenyglycine (d-, l-PG), and the unnatural amino acid amides d-, l-phenylglycine amide (d-, l-PG-NH2) and l-valine amide (l-Val-NH2) was studied in Pseudomonas putida ATCC 12633. The organism possessed constitutive l-amidase activities towards l-PG-NH2 and l-Val-NH2, both following the same pattern of expression, suggesting the involvement of similarly regulated enzymes, or a common enzyme. Quite surprisingly, growth in mineral media with l-PG-NH2 resulted in variable, long lag phases of growth and strongly reduced l-amidase activities. Conversion of d-PG-NH2 into d-PG and l-PG also occurred and could be attributed to the presence of an inducible d-amidase and the racemization of the amino acid amide in combination with l-amidase activity, respectively. The further degradation of l-PG and d-PG involved constitutive l-PG aminotransferase and inducible d-PG dehydrogenase activities, respectively, both with a high degree of enantioselectivity. Amino acid racemase activity for d- and l-PG was not detected.