Nitrilase and nitrile hydratase from Pseudomonas sp. UW4

Having just finished a project where we looked at a range of nitrilases and what their preferred substrates are, it is always interesting to ponder what the bacterium actually wanted the enzyme for (as compared to the host of xenobiotics you threw at it). We have often had the situation where we have an enzyme which we reckon ought to be active but doesn't seem interested in any of the forty or so compounds we have in our simple screen.
There is a recent paper in Applied and Environmental Microbiology by Duca, Rose and Glick which is concerned with investigating the biosynthesis of indoleacetic acid (IAA), which is a plant growth hormone. This compound comes from indoleacetonitrile (IAN) and there are two obvious pathways to get from there to IAA- via the NHase and via a nitrilase. These workers cloned both enzymes in to E. coli, and then looked at their level of interest in IAN. Interestingly the nitrilase had a habit of producing a proportion of amide as well as the usual acid. Also of interest is that the enzymes have different pH and temperature optima (Nase like 50 degrees C and pH6, the iron-centred NHase likes 4 degrees C and pH7.5), though I wonder if the lower temperature for the NHase is due to the fundamental lack of stability of iron NHases rather than an adaption. Additionally, the authors use some bioinformatics to confirm their experimental findings that this is an aromatic nitrile active system.