queuine synthase (incorrect as queuine is not the product);
queuine:NADP+ oxidoreductase (incorrect as queuine is not the product)
Acting on other nitrogenous compounds as donors;
With NAD+ or NADP+ as acceptor
The reaction occurs in the reverse direction. This enzyme catalyses one of the early steps in the synthesis of queuosine (Q-tRNA), and is followed by the action of EC 188.8.131.52, tRNA-guanosine34 transglycosylase. Queuosine is found in the wobble position of tRNAGUN in Eukarya and Bacteria  and is thought to be involved in translational modulation. The enzyme is not a GTP cyclohydrolase, as was thought previously based on sequence-homology studies.