Manganese biological function

Crystal structures of manganese catalases (in the (111)2 oxidation state) from Lactobacillus plantarum,its azide-inhibited complex, " and from Thermus thermophilus have been determined. There are differences between the structures that may reflect distinct biological functions for the two enzymes, the L. plantarum enzyme functions only as a catalase, while the T. thermo-philus enzyme may function as a catalase/peroxidase. The active sites are conserved in the two enzymes and are shown schematically in Figure 32. Each subunit contains an Mu2 active site,... 

A description of the most important properties of elements of interest, because they are essential for (or toxic to) life, is given in this section. A preliminary outline of biological function and level of toxicity is provided in Table 9.1. Those elements listed in the table that are more toxic to animals than to plants present the most insidious hazard to human health because the elements may accumulate in apparently healthy plants to levels that are poisonous to humans and animals. That is, for such elements the plant fails to play the role of a biological alarm that would warn of toxicity. The rating of elemental phytotoxidty in Table 9.1 should not be confused with the actual likelihood or frequency of toxicity in the field. For example, manganese is rated to have a fairly low intrinsic toxicity to plants, yet its toxicity is commonly seen because very high Mn concentrations can develop in wet soils. In contrast, chromium and lead are rated as more phytotoxic, but they are generally so insoluble in soils that toxicity from these metals is rarely seen. 

E S R.. Fenton. Transferrin Complexes with Non-Physiological and Toxic Metals, David M. Taylor. Transferrins, Edward N. Baker. Galactose Oxidase, Peter Knowles and Nobutoshi Ito. Chemistry of Aqua Ions of Biological Importance, David T. Richens. From a Structural Perspective Structure and Function of Manganese - Containing Biomolecules, David C. Weatherburn, Index. Volume 3,1996,304 pp. 109.50/ 70.00 ISBN 1-55938-642-8... 

The very important role of the heme system, Fe(Proto)LL ( 3) in biological oxygen transport and consumption as well as electron transport is a main topic not only of biochemists, but of bioinorganic chemists and biomimetic chemists as well for this general topic, the reader may consult some recent review articles [14-21,22]. Bioinorganic chemists have studied the effect of replacement of iron by other 3d metals, especially chromium, manganese, and cobalt, and frequently, interesting structural, spectral, or functional models [14,20] of the heme enzymes have been found with these metals. 

The most common metal encountered in electron transfer systems is iron, although copper and manganese play vital functions. Merely to emphasise the complexity of the catalysts that are used in biology, the structures of the active sites of ascorbate oxidase (Fig. 10-11) and superoxide dismutase (Fig. 10-12) are presented. It is clear that we have only just begun to understand the exact ways in which metal ions are used to control the reactivity of small molecules in biological systems. 

---