Binds Zn2+. Isolated from the bacteria?Bacillus subtilis?and?Escherichia coli. The reaction is part of the biosynthesis pathway of queuosine. The enzyme from?Escherichia coli?can also convert 6-pyruvoyl-5,6,7,8-tetrahydropterin and sepiapterin to 6-carboxy-5,6,7,8-tetrahydropterin [1].