A polypeptide having a novel endoribonuclease activity; a nucleic acid encoding the polypeptide; recombinant DNA having the nucleic acid therein; a transformant transformed with the recombinant DNA; a process for producing the polypeptide comprising the steps of cultivating the transformant and collecting the polypeptide from the culture; a process for producing a digest of single-stranded RNA comprising the step of reacting the polypeptide with the single-stranded RNA; and a method for the digestion of single-stranded RNA.