Endoribonuclease that initiates mRNA decay (By similarity). In vitro, catalyzes the hydrolysis of both 2',3'-cyclic AMP and 2',3'-cyclic GMP into 3'-AMP and 3'-GMP, respectively, at the 3'-terminal of RNA. Activates sarZ and agr operon resulting in the expression of virulence genes such as hemolysin, DNase and protease. Contributes to virulence in both silkworm-infection model and mice. Optimum pH is 9.0. Homodimer (Probable). Component of a possible RNA degradosome complex composed of cshA, eno, pfkA, pnp, rnjA, rnjB, rnpA and rny. Interacts specifically with RNA helicase CshA and enolase. No visible phenotype. Belongs to the RNase Y family.