Portuguese roadie Cabreira suspended for alleged masking

It's hard to imagine anyone slipping a protease molecule into a dope-test sample and getting away with it, given how closely these things are "managed", but apparently it can happen. Well he'll be appealing, and here it is:Former LA-MSS rider and Portuguese road champion João Cabreira was suspended for two years for "tampering with a doping control sample", the Portuguese Cycling Federation announced Friday. The rider is the first to be suspended for a long-suspected technique of using an enzyme called protease to break down products such as EPO in the urine to cheat a doping control.

So what is "protease"? Well it's being a bit vague and mis-informative to say it's "an enzyme called protease", in fact it will be a specific hydrolase enzyme that targets a protein in the EPO molecule and breaks it down, just like molecules in your body break down, for example, food. Wikipedia says: A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain, which form a molecule of protein.

Why would an athlete use it? It was probably added to the urine sample post-micturition, hence the tampering allegation. A cyclist or other sportsperson may use it to break down (and thus mask) a banned substance such as EPO. By breaking down or digesting the target protein the banned substance becomes undetectable (at least in and of itself, as fragments or by-products of that protein may be detectable, and the absence of natural EPO would be suspicious).