GENES AND ENZYMES OF THE ACETYL CYCLE OF ARGININE-BIOSYNTHESIS IN CORYNEBACTERIUM-GLUTAMICUM - ENZYME EVOLUTION IN THE EARLY STEPS OF THE ARGININE PATHWAY

A cluster of arginine biosynthetic genes of Corynebacterium glutamicum ATCC 13032, comprising argJ, argB and argD as well as part of argC an d argF, has been cloned by heterologous complementation of an Escheric hia coli argE mutant. The gene order has been established as argCJBDF by sequencing the entire 4.4 kb cloned DNA fragment. The C. glutamicum argB gene can be transcribed in E. coli cells from an internal promot er located in the coding part of the preceding argJ gene, whereas tran scription of the argJ gene appears vector-dependent. Expression of the corynebacterial argB gene is repressed by arginine in the native host but not in recombinant E. coli cells. Feedback inhibition of the corr esponding N-acetylglutamate kinase activity was observed both in cell extracts of C. glutamicum and in recombinant E. coil argB auxotrophic strains. Extracts of E. coli cells carrying cloned corynebacterial DNA display an ornithine acetyltransferase activity (encoded by argJ) whi ch alleviates the acetylornithinase (encoded by argE) deficiency of th e enterobacterial host. In contrast to Bacillus stearothermophilus orn ithine acetyltransferase which also exhibits acetylglutamate synthase activity, C. glutamicum ornithine acetyltransferase appears monofuncti onal. ArgA and ArgB proteins from different sources share highly signi ficant similarities. The evolutionary implications of these data are d iscussed.