PreQ1 synthase () is an enzyme that catalyzes the chemical reaction
The substrates of this enzyme are 7-cyano-7-deazaguanine, reduced nicotinamide adenine dinucleotide phosphate (NADPH), and two protons. Its products are 7-aminomethyl-7-deazaguanine and oxidised NADP<sup>+</sup>.
This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 7-aminomethyl-7-carbaguanine:NADP+ oxidoreductase. Other names in common use include YkvM, QueF, preQ0 reductase, preQ0 oxidoreductase, 7-cyano-7-deazaguanine reductase, 7-aminomethyl-7-carbaguanine:NADP+ oxidoreductase, queuine synthase and queuine:NADP+ oxidoreductase: (the last two are misleading as queuine is not the product). The enzyme is part of the biosynthetic pathway to modified nucleoside, queuosine. , this was the only enzyme known to directly catalyze the reduction of a nitrile group to a primary amine.