I've been looking through PDB — the Protein Data Bank — and I noticed that the protein with the most structures is human carbonic anhydrase II (UniProt: P00918), with over a thousand X-ray structures.
This seems surprising to me, as carbonic anhydrase is a zinc-containing enzyme which catalyses a really simple reaction, and doesn’t seem to be part of any key signalling pathways. In terms of relevance to disease or as a drug target, all I could find was on DrugBank was a few glaucoma drugs which have this as their target (diclofenamide, methazolamide, acetazolamide), and those are really old (60 years).
So, what is it about carbonic anhydrase that makes it so interesting? Is it that more or better drugs are needed to target it? (For what disease?) Is it that it’s a really interesting scientific model of a metalloenzyme? Or something else?