Organization of genes responsible for the stereospecific conversion of hydantoins to α-amino acids in Arthrobacter aurescens DSM 3747

Abstract.

Arthrobacter aurescens DSM 3747 hydrolyzes stereospecifically 5′-monosubstituted hydantoins to α-amino acids. The genes involved in hydantoin utilization (hyu) were isolated on an 8.7-kb DNA fragment, and by DNA sequence analysis eight ORFs were identified. The hyu gene cluster includes four genes: hyuP encoding a putative transport protein, the hydantoin racemase gene hyuA, the hydantoinase gene hyuH, and the carbamoylase gene hyuC. The four genes are transcribed in the same direction. Upstream of hyuP and in opposite orientation to the hyu genes, three ORFs were found showing similarities to cytochrome P450 monooxygenase (ORF1, incomplete), to membrane proteins (ORF2), and to ferredoxin (ORF3). ORF8 was found downstream of hyuC and again in opposite orientation to the hyu genes. The gene product of ORF8 displayed similarities to the LacI/GalR family of transcriptional regulators. Reverse transcriptase PCR experiments and Northern blot analysis revealed that the genes hyuPAHC are coexpressed in A. aurescens after induction with 3-N-CH₃-IMH. The expression of the hyu operon was not regulated by the putative regulator ORF8 as shown by gene disruption and mobility-shift experiments.