Arginase manganese

The importance of manganese for bacteria, such as that of Ni and to a lesser extent Co, as we saw in the last chapter, is considerable. Of course, as we will see shortly, it is also important in the tetranuclear Mn cluster that is involved in oxygen production in photosynthetic plants, algae and cyanobacteria, as well as in a number of mammalian enzymes such as arginase and mitochondrial superoxide dismutase. Most of manganese biochemistry can be explained on the one hand by its redox activity, and on the other by its analogy to Mg2+ (reviewed in Yocum and Pecoraro, 1999). 

We begin this overview of manganese biochemistry with a brief account of its role in the detoxification of free radicals, before considering the function of a dinuclear Mn(II) active site in the important eukaryotic urea cycle enzyme arginase. We then pass in review a few microbial Mn-containing enzymes involved in intermediary metabolism, and conclude with the very exciting recent results on the structure and function of the catalytic manganese cluster involved in the photosynthetic oxidation of water. 

Manganese Unrefined cereals nuts leafy vegetables tea Component of some enzymes glycosyl hansferase, arginase, pyruvate carboxylase... 

Figure 31 Schematic view of the manganese binding in arginase.

V. MANGANESE CATALASE AND CATALASE-TYPE ACTIVITY OF ARGINASE... 

Not surprisingly, both manganese ions are necessary for the catalase activity of arginase, as confirmed by metal replacement experiments in a mutant arginase. Indeed, whereas the hydrolytic reaction was restored upon binding one Cd2+ ion to form a heteronuclear MnCd enzyme, catalase activity was not [111]. 

B contains significant amounts of manganese. The EPR data [171] suggest the presence in protein B of a spin-coupled dinuclear Mn11 cluster, perhaps of the type found in catalases and arginases. No additional information about the metal active site is currently available. 

Manganese The human body is estimated to contain a total of 10-20 mg Mn. The RDA is between 2 and 5 mg per day. Manganese is involved in many enzymatic processes as a metalloenzyme or as a cofactor. In contrast to the Mn-activated enzymes, there are few Mn metalloenzymes (arginase, pyruvate carboxilase, and Mn-superoxide dismutase) [14]. The content of Mn in milk responds rapidly to changes in dietary intakes of this metal. 

Brock, A-, Chapman, S., Ulman, E and Wu, C. (1994). Dietary manganese deficiency decreases rat hepatic arginase activity /. Nirfr 124, 340-344. 

Kanyo ZF, Scolnick LR, Ash DE, Christianson DW. Structure of a unique binuclear manganese cluster in arginase. Nature 1996 383 554-7. 

Lombeck I, Wendel U, Versieck J, van Ballenberghe L, Bremer HJ, Duran R, Wadman S. Increased manganese content and reduced arginase activity in erythrocytes of a patient with prolidase deficiency (iminodipeptiduria), Eur J Pediatr 1986 144 571-3. 

The major role of manganese in biology is in oxygen production by photosynthetic plants, algae, and cyanobacteria. It is also involved in a number of mammalian enzymes like arginase and mitochondrial superoxide dismutase and it also plays an important role in microbial metabolism. Most of manganese biochemistry can be... 

There is manganese in glutamine synthetase, an important brain enzyme in arginase, which changes one amino acid into a dif-... 

Carl GF, Blackwell LK, Barnett EC, et al. 1993. Manganese and epilepsy Brain glutamine synthetase and liver arginase activities in genetically epilepsy prone and chronically seizured rats. Epilepsia 34 441-446. 

Kuhn NJ, Ward S, Piponski M, et al. 1995. Purification of human hepatic arginase and its manganese (Il)-dependent and pH-dependent interconversion between active and inactive forms A possible pH sensing function of the enzyme on the ornithine cycle. Arch Biochem Biophys 320 24-34. 

One particularly key metallohydrolase that contains manganese is the enzyme arginase (4-7), an enzyme for which a crystal structure... 

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