How many actual phosphorylation sites are there?

We've seen some amazing papers that have identified 10s of thousands of phosphopeptides. Numbers that are boggling in size and can seem kind of unbelievable.

Ever wondered how many sites could possibly exist? Wonder no longer, cause this team did the hard math in this new open access paper in GigaScience(?)!

To get their numbers they pulled 1,000 papers. Not kidding, that's what they said. They narrowed the papers down to a smaller subset of experiments -- they looked at 97 human studies and did curve-fitting stuff to the data. They look at other organisms, but they have the most data points to work on from human studies.

Their results, in a nutshell, we may still have a long way to go before we identify every human phosphopeptide -- current technology may be able to find about 40-60% (and you know the ones we haven't found yet aren't gonna be easy).

However, we've probably identified most proteins that can be phosphorylated! It sounds like finding the other sites on these proteins is what is needed at this point.

Are they right? I'm certainly not qualified to answer that, but it does help put the numbers in perspective!