Characterization of the Ornithine Hydroxylation Step in Albachelin Biosynthesis.

Kendra Bufkin,Pablo Sobrado

doi:10.3390/molecules22101652

Abstract

N-Hydroxylating monooxygenases (NMOs) are involved in siderophore biosynthesis. Siderophores are high affinity iron chelators composed of catechol and hydroxamate functional groups that are synthesized and secreted by microorganisms and plants. Recently, a new siderophore named albachelin was isolated from a culture of Amycolatopsis alba growing under iron-limiting conditions. This work focuses on the expression, purification, and characterization of the NMO, abachelin monooxygenase (AMO) from A. alba. This enzyme was purified and characterized in its holo (FAD-bound) and apo (FAD-free) forms. The apo-AMO could be reconstituted by addition of free FAD. The two forms of AMO hydroxylate ornithine, while lysine increases oxidase activity but is not hydroxylated and display low affinity for NADPH.

Highlights

The actinomycetes Amycolatopsis alba produces the siderophore albachelin under iron-limiting conditions
Albachelin is a hydroxamate-containing siderophore composed of a linear peptide of 6 amino acids: N-α-acetyl-N-δ-hydroxy-N-δ-formylornithine, N-α-methyl-N-δ-hydroxyornithine, cyclic N-hydroxyornithine, and three molecules of serine (Scheme 1)
The operon that codes for the enzymes in albachelin biosynthesis includes a putative flavin-dependent ornithine monoxygenase [1]. We refer to this enzyme as albachelin monooxygenase (AMO) (Scheme 1)

Summary

Introduction

The actinomycetes Amycolatopsis alba produces the siderophore albachelin under iron-limiting conditions. Albachelin is a hydroxamate-containing siderophore composed of a linear peptide of 6 amino acids: N-α-acetyl-N-δ-hydroxy-N-δ-formylornithine, N-α-methyl-N-δ-hydroxyornithine, cyclic N-hydroxyornithine, and three molecules of serine (Scheme 1). Ornithine and its derivatives make up the backbone of the peptide and coordinate the iron. The operon that codes for the enzymes in albachelin biosynthesis includes a putative flavin-dependent ornithine monoxygenase [1]. We refer to this enzyme as albachelin monooxygenase (AMO) (Scheme 1).

Methods

Results

Conclusion