Histidine biosynthetic pathway in Staphylococcus aureus

Abstract

The enzymes involved in histidine biosynthesis and their metabolic control are similar in Staphylococcus aureus and other organisms which have been studied, although some of these enzymes in S. aureus appear to be more labile. As is true in Salmonella typhimurium, the imidazoleglycerol phosphate dehydratase of S. aureus is inhibited in vitro by 4-amino-1,2,4-triazole (amitrole). Unlike S. typhimurium, however, growth in the presence of amitrole does not result in derepression of the histidine biosynthetic enzymes, and as a consequence the inhibition of the growth of S. aureus by amitrole is not overcome. This observation provided the basis for isolating mutants of S. aureus which were resistant to amitrole. Most of these amitrole-resistant mutants possessed constitutively high levels of the histidine biosynthetic enzymes, and the levels of these enzymes were not repressed in most of these mutants when they were grown in excess L-histidine.