Molybdenum mammals

Trace quantities of molybdenum are beneficial and perhaps essential for normal growth and development of plants and animals. In mammals, molybdenum can protect against poisoning by copper, mercury, and probably other metals, and may have anticarcino-genic properties. For all organisms, the interpretation of molybdenum residues depends on knowledge of molybdenum, copper, and... 

Molybdenum. Molybdenum is a component of the metaHoen2ymes xanthine oxidase, aldehyde oxidase, and sulfite oxidase in mammals (130). Two other molybdenum metaHoen2ymes present in nitrifying bacteria have been characteri2ed nitrogenase and nitrate reductase (131). The molybdenum in the oxidases, is involved in redox reactions. The heme iron in sulfite oxidase also is involved in electron transfer (132). 

Copper deficiency in humans and other mammals is characterized by slow growth, hair loss, anemia, weight loss, emaciation, edema, altered ratios of dietary copper to molybdenum and other metals, impaired immune response, decreased cytochrome oxidase activity, central nervous system histopathology, decreased phospholipid synthesis, fetal absorption, and eventually death (NAS 1977 Gallagher 1979 Kirchgessner et al. 1979 USEPA 1980 ATSDR 1990 Percival 1995). 

Table 30.4 Molybdenum Effects on Selected Species of Mammals...

Molybdenum is essential for a number of enzymes, for example xanthine oxidases in mammals and nitrogenases in nitrogen-fixing bacteria. 

The oxo-transfer chemistry of molybdenum in sulfite oxidase is probably the best characterized, in terms of synthetic models, structural and mechanistic data, of all the elements we have described up till now. The reaction cycle (Figure 17.5) involves binding of sulfite to the oxidized MoVI, two-electron reduction of the Mo centre and release of sulfate. The Movl centre is restored by successive one-electron transfers from a cytochrome (bs in mammals). The primary oxo-transfer reaction ... 

Molybdenum is required in the diet. It is required by three enzymes in mammals sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. Molybdenum occurs in these enzymes as part of the molybdenum cofactor (Figure 10.52). This cofactOT is biosynthes z.ed in the body with GTP as the starling material. All known Mo mclalloenzymes, with the exception of nitrogenase (a plant enzyme), use Mo in the form of the molybdenum cofactor. 

Molybdenum chemistry is complex and inadequately known. Its toxicological properties in mammals are governed to a remarkable extent through interaction with copper and sulfur residues of molybdenum alone are not sufficient to diagnose molybdenum poisoning. 

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