Genetic and chemical studies relating to α-aminoisobutyri acid (AIB) metabolism

Abstract

The non-protein amino acid a-aminoisobutyric acid (Aib) occurs naturally in soil. Burkholderia cepacia utilizes Aib as a sole nitrogen source by virtue of a 2,2-dialkylglycine decarboxylase, which is encoded by the dgdA gene. In this study, 30 prokaryotes were cultured on minimal media containing Aib as the sole nitrogen source and identified by 16S rRNA gene sequencing. Several attempts were made to clone dgd genes from these organisms. Plasmid libraries were constructed in E. coli from DNA isolated from four Aib-utilizing bacteria. Libraries were screened for clones which demonstrated the ability to grow on Aib containing media and therefore contained cloned dgd genes. Sequence analysis of plasmids isolated from Aib utilizing clones revealed no similarity to dgd genes from B. cepacia. Also, 4-methyl-2-(4-nitrophenyl)-5(4H)-oxazolone was alkylated at the 4-position with various alkyl halides. This was the key step in synthesis of disubstituted N-p-nitrobenzoyl-DL-glycines, which are precursors to 2,2-dialkylglycines. Synthesis was performed in multiple steps. N-p-nitrobenzoyl-DL-alanine was synthesized by aminolysis of DL-alanine with benzoyl chloride. The 4-methyl-2-(4-nitrophenyl)-5(4H)-oxazolone was synthesized by dehydration of N-p-nitrobenzoyl-DL-alanine with acetic anhydride. Alkylation of 4-methyl-2-(4-nitrophenyl)-5(4H)-oxazolone was performed by adding base, which made the oxazolone enolate, and alkyl halide, which participated in SN2 reactions with the enolate. Substituted oxazolones were hydrolyzed into disubstituted N-p-nitrobenzoyl-DL-glycines with DCl.