Picornain 3C-like protease is a thiol protease that probably cleaves the polyprotein. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Specific enzymatic cleavages by picornain 3C-like protease in vivo yield mature proteins. Picornain 3C-like protease is autocatalytically processed (By similarity).