Cobalt:B₁₂Enzymes & Coenzymes

Abstract

The most prominent biological role associated with cobalt concerns vitamin B 12 , its natural variants, and its coenzyme forms. The B 12 ‐derivatives are cobalt complexes of the unique and remarkably complex corrin ligand that belong to the larger class of the tetrapyrrolic natural compounds. The ‘antipernicious anemia factor’ vitamin B 12 and its cofactor forms are, first of all, required for human and animal health. However, except for the higher plants, all forms of life appear to depend upon the natural variants of vitamin B 12 . The main chemical reactivities of the corrinoids (needed to fulfill their essential biological roles) may reflect their possible corresponding chemical contributions to the development of the early stages of life on earth. Indeed, the corrinoids play a particularly basic role in carbon metabolism in microorganisms, which also are the only natural sources of the B 12 ‐derivatives. Microorganisms have developed extraordinary means for the biosynthesis, and for the regulation of the biosynthesis of the B 12 ‐derivatives, in order to cope with the structural and functional complexity of these tetrapyrrolic cobalt‐compounds, while most (other) forms of life have evolved intricate strategies for the economic and efficient uptake and transport of the corrinoids. The known cofactor functions of the cobalt‐corrinoids are due to their extraordinary organometallic chemistry and their redox chemistry under physiological conditions: Coenzyme B 12 , methylcorrinoids, and reduced corrinoids are the cofactors in various important and unique organometallic enzymes, whose intricate structural and mechanistic properties are the current focus of strong and broad research activities. The essential role of the corrinoids in the remarkable organometallic paths of carbon fixation and further carbon metabolism in anaerobic microorganisms has attracted particular attention. Vitamin B 12 and its derivatives thus hold an important position in all of the life sciences and are at the center of particular interdisciplinary interest from such diverse areas as medicine, biology, chemistry, and physics.

Effect of Cobalt, Nickel, and Selenium/Tungsten Deficiency on Mesophilic Anaerobic Digestion of Chemically Defined Soluble Organic Compounds

“…As Co is an essential component in many enzymes [7,8], the insignificant effect on process performance after its depletion indicates the possibility that sufficient amount of Co was entering the reactor with substrate components. An analysis of the Co content in different substrate components revealed that particularly casein contained Co (contributing around 540 ngCo L substrate −1 ; Table 1).…”

“…Availability of specific trace elements (TEs), which serve as micronutrients for the growth and activity of microorganisms at different stages of AD, is central for the efficiency and stability of AD processes [4][5][6]. Cobalt (Co) is essential for the functioning of acetogens and methanogens due to its involvement in cobamide coenzymes, responsible for methyl group transfers [7,8]. Nickel (Ni) is vital for methanogenesis due to its functional role in porphyrinoid F 430 , a prosthetic group of the active site of methyl coenzyme M reductase, which catalyses the formation of methane [9].…”

Quinone-fused porphyrins as contrast agents for photoacoustic imaging

“…Alternative coloured pigments are tetrapyrroles, which act as key ligands in many biologically active complexes, such as oxygen binding heme, light harvesting photosystems in chlorophyll and redox reactions in cytochromes. Thus, this class has been intensely studied for bioinorganic, 9 medicinal 10 and material applications. 11 Porphyrins show strong absorption, in particular for visible wavelengths, and fluorescence emission in the red to near infrared (NIR) range.…”