A spectrophotometric assay for the degradation of the siderophore deferrioxamine B

A spectrophotometric assay using ferric perchlorate in a perchloric acid solution has been developed to monitor the degration of the trihydroxamate siderophore deferrioxamine B to monohydroxamates. Using the ferric perchlorate solution and employing various concentrations of acetohydroxamic acid (as the model monohydroxamic acid) while maintaining a constant amount of deferrioxamine B resulted in the shifting of the absorption maximum from that of ferrioxamine B to longer wavelengths and toward that of a pure ferri-acetomonohydroxamic acid solution. A similar result was noted when a cell-free extract, from a bacterium capable of usig deferrioxamine B as its sole carbon source, was given the siderophore in a phosphate buffer and aliquots of the enzyme-deferionxamine B solution were removed for analysis. The assay may thus be used to monitor the formation of the monohydroxamic acid degradation products of the siderophore by the enzyme(s) in the cell-free extract.