Molybdenum cofactor Moco

Fig. 5.10. The formula of one of the mononuclear molybdenum cofactors, Moco. Others have a nucleotide phosphate extension (see references to these elements in Further Reading). In sulfide-rich environments, tungsten replaced molybdenum. In some coenzymes, two pterins are bound to the metal ions.

The molybdenum cofactor (Moco) is the essential component of a group of redox enzymes [20-22], which are diverse not only in terms of their phylogenetic distri-... 

METHOD OF CONTINUOUS VARIATION MOLYBDENUM COFACTOR (MoCo) Molybdenum-dependent reactions, ALDEHYDE OXIDASE MOLYBDOPTERIN NITRATE REDUCTASE NITROGENASE SULFITE OXIDASE XANTHINE DEHYDROGENASE MOLYBDOPTERIN... 

Synthetic and structural aspects about the extremely labile molybdenum cofactor (Moco) have been summarized <93H(35)l55l> and indicate fundamental difficulties in building up the molybdenum enedithiole complex. 

Enzymes containing molybdenum are of two types (1) Nitrogenases, which are required for converting atmospheric nitrogen to nitrogen compounds (NH3, for example) nitrogenases contain a characteristic polymetal atom cluster species called the iron-molybdenum cofactor, FeMoco (Section 17-E-10). (2) The other Mo enzymes, all of which have some variant of a characteristic molybdenum cofactor, Moco. 

The presence of a pterin-dithiolene (MPT-based) ligand at Mo is the unifying feature of the various molybdenum cofactors (Moco s) and enzymes. " The chemical nature of the pterin-dithiolene ligand was defined by degradative and spectroscopic studies performed by Rajagopalan, Johnson, and coworkers. They proposed the bicyclic structure (4) and... 

This chapter gives an overview of the biosynthesis of THF, (6if)-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4), and molybdopterin (MPT), the organic compound of the molybdenum cofactor (Moco), and discusses the enzymoiogy of the proteins that bind the three classes of cofactors (structures are shown in Scheme 1). The biosynthesis of THF, BH4, and MPT start from guanosine triphosphate (GTP), but the reactions for the conversion of GTP into the three cofactors are diverse and involve different enzymatic compounds. 

Molybdenum (see also Part III, Chapter 18) The molybdenum cofactor (MoCo) is an essential component of a large family of enzymes involved in important transformations in carbon, nitrogen, and sulfur metabolism. The MoCo biosynthetic pathway is evolutionarily conserved and found in arch-aea, eubacteria, and eucaryotes. In humans. 

R. R. Mendel and G. Schwarz, Biosynthesis and Molecular Biology of the Molybdenum Cofactor (Moco), in Metal Ions in Biological Systems , eds. A. Sigel and H. Sigel, Marcel Dekker, New York, 2002, Vol. 39, p. 317. 

Molybdenum is largely used in steel industry. Its compounds are widely used in coloring agents, solid lubricants and as catalysts. Molybdenum is an essential trace element and a component of xanthine oxidase. This enzyme catalyzes the formation of urate. Molybdenum cofactor (Moco)-defi-ciency is a lethal autosomal recessive disease. Moco-deficiency in humans can cause neurological damage, seizures and various brain dysmorphisms. 

The molybdenum cofactor (Moco) is an extraordinary molecule in biology. As a small metal-containing compound, it has the unprecedented combination of a dithiolene chelate for metal binding and a pterin appended to a pyran ring. The resultant cofactor is electronically nimble due to the presence of three redox active moieties, ie. the molybdenum atom, the dithiolene and the pterin, which in concert can support a range of redox events. 

Figure 1.1 The molybdenum cofactor (Moco), comprised of a Mo ion bound to a pyranopterin dithiolene (PDT) chelate. Note that the PDT shown here is in the fully reduced tetrahydro oxidation state. ...

Figure 2.1 Left the pyranopterin dithiolene (PDT). Right one form of the molybdenum cofactor (Moco).

---