Biochemical aspects of molybdenum coordination chemistry

The Coordination and Bioinorganic Chemistry of Molybdenum

Publisher Summary This chapter reviews the structure and mechanism of nitrate reductases and presents the distinction between two main types of nitrate reductases on a phylogenetic basis, namely: the eukaryotic type and one (or possibly more) prokaryotic types. The most critical and least understood aspects of the biochemistry of nitrate reduction are the electronic events associated with the production of nitrite from nitrate at the molybdenum center. The eukaryotic forms of nitrate reductases are reported to lie in the molecular weight range between 160,000 and 500,000; although the elliptical shape of the enzyme, as shown by its anomalous behavior on sucrose density centrifugation and gel filtration, requires that more than one method of molecular weight estimation be used to determine the true value. The presence of subunits is characteristic of all the eukaryotic forms of the enzyme studied to date but their sizes and probable numbers differ quite widely. For the prokaryotic, the molecular weight of the purified terminal moieties obtained from prokaryotic sources range from 69,000 to 880,000. Subunit compositions for these are complex and not consistent in terms either of methods of dissociation or of different preparations from separate laboratories.

R.J.P. Williams

Papers

Reactions of molybdenum compounds with riboflavin.