3A15

Aldoxime dehydratase (Oxd) is a heme-containing enzyme that catalyses the dehydration of aldoximes (R–CHN–OH) to the corresponding nitrile (R–C'N). Some species of microbes utilise an aldoxime-nitrile pathway, metabolising aldoximes to the corresponding carboxylic acids through nitriles formed by dehydration of aldoximes with aldoxime dehydratase. There are two pathways for the conversion of nitriles to carboxylic acids, i) the hydrolysis of nitriles by nitrilase, and ii) the sequential actions of nitrile hydratase and amidase. Nitriles are important for biological self-defence mechanisms, and are also of interest as intermediates in some industrial processes.

The dehydration reaction proceeds only via N-coordinated substrate in the ferrous heme. The organic substrate is shown by crystallographic and spectroscopic data to be directly coordinated to the heme iron in dehydration of aldoxime, which is a unique example among heme enzymes