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Monday 13 August 2012

Looking for nitrile active enzymes

I was out for a walk at the weekend at Bishop Middleham quarry which is a nature reserve and an example of Magnesian limestone grassland. It is a nice spot and very quiet so there is plenty of wildlife to look at. One thing we spotted fluttering all around the grassland on the quarry floor was a six spotted burnet moth, Zygaena filipendulae. After a bit we got one to settle and we got a photo.

All very ecological but what's this got to do with nitrile hydratase? I know nothing about moths, so I looked this up when we got him to identify it. The intriguing thing about this moth is that it survives in the wild despite not being at all camouflaged (it is a blur of metallic grey, red and orange on the wing). Its defence strategy is based on containing cyanogenic glucosides which liberate HCN given half a chance making them a very poor choice of meal for anything tempted to snack on them. A browse of the literature suggests that it gets its cyanide both from absorption from its food source when a larva (such as bird's foot trefoil) and also biosynthesis. It seemed logical to me that if it has something to make nitriles, it might have some pathway to dispose of them too so that its biochemistry doesnt get swamped.
Rather amazingly a genome search of NCBI shows that Zygaena filipendulae has had its transcriptome sequenced. Apparently there are all sorts of biosynthetic apparatus for making cyanogenic compounds in there but when I did a bit of BLASTing nothing that looked vaguely like a nitrile hydratase. Maybe there are nitrile hydratase enzymes in the intestinal flora of this moth and its larva. That hasnt been examined yet!

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