Catalyzes the hydrolysis of queuosine 5′-phosphate, releasing the nucleobase queuine (q). Is required for salvage of queuine from exogenous queuosine (Q) that is imported and then converted to queuosine 5′-phosphate intracellularly. In vitro, can also catalyze the release of the q base directly from Q as substrate; however, it was shown that Q is not the biologically relevant substrate. Shows a very low activity on queuosine 3′,5′-diphosphate, and cannot release q from queuosine 3′-phosphate and from the 5′-nucleotides AMP, UMP, CMP or GMP, indicating specificity for the queuine base (PubMed:36610787). Can complement the yeast mutant SPAC589.05c, restoring Q incorporation into tRNA (PubMed:24911101).
