The Role of System-Specific Molecular Chaperones in the Maturation of Molybdoenzymes in Bacteria

Figure 1

The biosynthesis of Moco and the families of molybdoenzymes. Shown is a scheme of the biosynthetic pathway of Moco from MPT in bacteria. The proteins involved in the reactions are colored red. In bacteria, Mo-MPT can be further modified by the MobA function which attaches GMP to the phosphate group of MPT, forming MGD, and two equivalents of MGD are bound to molybdenum, forming the so-called bis-MGD cofactor. For enzymes of the xanthine oxidase family, Mo-MPT or MCD (which is synthesized by the MocA protein by the attachment of CMP to Mo-MPT) can be modified by the replacement of one oxo-ligand by a sulfur ligand while forming the mono-oxo Moco. This reaction is catalyzed by a NifS-like protein in bacteria. The three molybdenum-containing enzyme families are divided into the DMSO reductase, the sulfite oxidase, and the xanthine oxidase families according to their active-site structures. The molybdenum center is shown in its oxidized state as Mo^VI. Moco is the general term for all different variants of the cofactor.