Manganese complexes amino acids

Metal-ion catalysis has been extensively reviewed (Martell, 1968 Bender, 1971). It appears that metal ions will not affect ester hydrolysis reactions unless there is a second co-ordination site in the molecule in addition to the carbonyl group. Hence, hydrolysis of the usual types of esters is not catadysed by metal ions, but hydrolysis of amino-acid esters is subject to catalysis, presumably by polarization of the carbonyl group (KroU, 1952). Cobalt (II), copper (II), and manganese (II) ions promote hydrolysis of glycine ethyl ester at pH 7-3-7-9 and 25°, conditions under which it is otherwise quite stable (Kroll, 1952). The rate constants have maximum values when the ratio of metal ion to ester concentration is unity. Consequently, the most active species is a 1 1 complex. The rate constant increases with the ability of the metal ion to complex with 2unines. The scheme of equation (30) was postulated. The rate of hydrolysis of glycine ethyl... 

It has been known for many years that the rate of hydrolysis of a-amino acid esters is enhanced by a variety of metal ions such as copper(II), nickel(II), magnesium(H), manganese(II), cobalt(II) and zinc(II).338 Early studies showed that glycine ester hydrolysis can be promoted by a tridentate copper(II) complex coupled by coordination of the amino group and hydrolysis by external hydroxide ion (Scheme 88).339 Also, bis(salicylaldehyde)copper(II) promotes terminal hydrolysis of the tripeptide glycylglycylglycine (equation 73).340 In this case the iV-terminal dipeptide fragment... 

Manganese(III) complexes of a-amino acids have been presented as structural models for the diffusible Mn ion of MnP [60],... 

It is difficult to estimate what the rate of the metal ion catalyzed oxidative deamination reaction of amino acids would be in natural waters. Hamilton and Revesz (30) found that the rate of oxidation of alanine in the presence of pyridoxal and manganese ions was inhibited by EDTA. Since metal ions in natural waters can be complexed by a variety of organic and inorganic compounds, their effectiveness in catalyzing the oxidative deamination of amino acids may be reduced. Also, the fraction of dissolved amino acids which would be complexed by metal ions at the pH and metal ion and amino acid concentrations found in natural waters must be considered. At neutral pH, where the amino group of the amino acid is protonated, the fraction of the amino acid that would be in the form of the metal ion complex depends upon the equilibrium constant for the formation of the complex and the pK of the amino proton of the amino acid. The reactions for the formation of the Cu2+-alanine complexes can be written as... 

SODs are differentiated mainly by the redox-active metal in the active site copper, manganese, or iron. The iron and manganese SODs are structurally similar (5-11) and are structurally distinct from the Cu,Zn SOD (12). The dramatic features of these enzymes are that they catalytically dismutate superoxide at rates that are not only diffusion controlled but have been shown to be electrostatically facilitated (13). In these systems, modifications of amino acid residues near the active site have been shown to alter the enzymatic activity, indicating that superoxide is electrostatically drawn into the active site channel (14). In addition, in contrast to the spontaneous dismutation rate of 02 and the dismutation rates of 02 by many metal complexes, all of which are pH dependent, the enzymatic dismutation rate is largely pH independent over the pH range (5-10). 

Manganese(tl) complexes,, 3, 9-82 acctylacetonates, 48 acetylides, 14 alcohols, 37 alkoxides, 37 alkyl phosphines, 13 alkyls, 12 amides, 15, 16 amine oxides, 39 amines, 16 amino acids, 43, 62 sulfur containing, 70 ammines, 15 antimony ligands, 31-34 arsenates, 4,5, 46 arsenic ligands, 31-34 arsenic oxides, 39 aryls, 12, 14 azides, 22 binary alkyls, 13 bipyridyl, 24, 25 anions, 25... 

Debus RJ. Amino acid residues that modulate the properties of tyrosine Y(Z) and the manganese cluster in the water oxidizing complex of photosystem II. Biochim Biophys Acta 2001 1503 164-86. 

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