MobA catalyzes the formation of molybdopterin guanine dinucleotide.
The prokaryotic enzyme molybdopterin-guanine dinucleotide biosynthesis protein A (MobA). All mononuclear molybdoenzymes bind molybdenum in complex with an organic cofactor termed molybdopterin (MPT). In many bacteria, including Escherichia coli, molybdopterin can be further modified by attachment of a GMP group to the terminal phosphate of molybdopterin to form molybdopterin guanine dinucleotide (MGD). This GMP attachment step is catalyzed by MobA, by linking a guanosine 5'-phosphate to MPT forming molybdopterin guanine dinucleotide. This reaction requires GTP, MgCl2, and the MPT form of the cofactor. It is a reaction unique to prokaryotes, and therefore may represent a potential drug target.