ABSTRACT
This chapter is divided into three sections: N-hydroxylases, N-acyltransferases, and siderophore synthetases. N-Acetyltransferases are widely spread enzymes involved in the biosynthesis and detoxification of endogenous compounds. The hydroxamic acid monomer as well as amino acids are activated, oligopeptides are formed, and the cyclohexapeptide is built in a cyclization reaction. Reactions of this kind are accomplished by multienzyme complexes as reported for fatty acid synthetases and nonribosomal peptide synthetases. The observation that a high concentration of iron suppresses the biosynthesis of siderophores was first reported by Garibaldi and Neilands, and the fact that low iron concentrations favor the biosynthesis of siderophores has been used for the production of siderophores in many microorganisms. Siderophore biosynthesis may be controlled by different strategies like the binding of an effector to a transcriptional activator or by acting at a posttranscriptional level by altering the rate of mRNA turnover.
