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Copper-histidine chelate

The copper(II) ion as well as a number of copper(II) chelates with incompletely filled coordination shells, e.g., the 1 1 chelates of 2,2 -dipyri-dyl, 1,10-phenanthroline, ethylenediamine, or histidine, were found to increase the rate of hydrolysis of diisopropylphosphorofluoridate, a cholin-... [Pg.223]

The P-alanyl dipeptides carnosine and anserine (A -methylcarnosine) (Figure 31-2) activate myosin ATPase, chelate copper, and enhance copper uptake. P-Alanyl-imidazole buffers the pH of anaerobically contracting skeletal muscle. Biosynthesis of carnosine is catalyzed by carnosine synthetase in a two-stage reaction that involves initial formation of an enzyme-bound acyl-adenylate of P-alanine and subsequent transfer of the P-alanyl moiety to L-histidine. [Pg.264]

Various spectroscopic methods have been used to probe the nature of the copper centers in the members of the blue copper oxidase family of proteins (e.g. see ref. 13). Prior to the X-ray determination of the structure of ascorbate oxidase in 1989, similarities in the EPR and UV-vis absorption spectra for the blue multi-copper oxidases including laccase and ceruloplasmin had been observed [14] and a number of general conclusions made for the copper centers in ceruloplasmin as shown in Table 1 [13,15]. It was known that six copper atoms were nondialyzable and not available to chelation directly by dithiocarbamate and these coppers were assumed to be tightly bound and/or buried in the protein. Two of the coppers have absorbance maxima around 610 nm and these were interpreted as blue type I coppers with cysteine and histidine ligands, and responsible for the pronounced color of the protein. However, they are not equivalent and one of them, thought to be involved in enzymatic activity, is reduced and reoxidized at a faster rate than the second (e.g. see ref. 16). There was general concurrence that there are two type HI... [Pg.54]

Mn2+, D.F.P.-ase is further activated by cysteine, histidine, thiolhistidine, and serine, histamine and 2 2 -dipyridyl. Reagents reacting with metal ions, SH groups and carbonyl groups inhibit D.F.P.-ase activity. Work is proceeding on the further elucidation of such mechanisms.1 In a somewhat similar connexion attention is called to the fact that the non-enzymic hydrolysis of D.F.P. is accelerated by heavy metals and their complexes, in particular by copper chelates of ethylene diamine, o-phenanthroline, 2 2 -dipyridyl and histidine.2... [Pg.88]

Substantial rate accelerations are observed in these systems for base hydrolysis. Thus for the ethylenediamine complex (18) rate increases of 4x 104 for GlyOEt to 1.4 x 107 for ethyl picolinate are observed.85 These rate accelerations are consistent with the formation of carbonyl-bonded species (18). The effects with methyl L-cysteinate and methyl L-histidinate are much less marked as such ligands can give mixed ligand complexes which do not involve alkoxycarbonyl donors. Thus in the case of methyl L-histidinate the complex (20) is formed. For these latter two esters only relatively small rate accelerations of 20-100 occur. For the chelate ester complexes, the ratios of kcm/kH2o fail within the range 3.8 x 109 to 3.2 x 1011. Such values for the relative nucleophilicity of water and hydroxide ion are comparable with those previously noted for copper(II) complexes.82... [Pg.423]

The copper chelate of albumin, which has copper bonded to a specific bonding site (histidine at position 3), has been shown to be a potent non-cyto-lytic antiproliferative agent [666]. This complex decreased phytohaemag-... [Pg.532]

These observations are also consistent with copper complex modulation of A terminal desaturase activity [702]. A purified chicken liver microsomal preparation of stearoyl-CoA A -desaturase was inhibited with Cu(IIXtyrosi-nate)j, Cu(II)(lysinate)2 and Cu(II)(histidinate)2. These chelates lowered the steady-state level of ferrocytochrome only 20% and only partially inhibited the NADH-ferricyanide reductase activity, indicating that the terminal desaturation step was being inhibited. Since oxygen is known to be involved in this desaturation and that there is an initial reduction of the desaturase iron, it is plausible that these chelates are decreasing desaturase activity by acting as superoxide scavengers [702]. [Pg.542]

The catalase-like action of hemocyanin is probably because of copper bound to one or more amino acids in the protein. Contrary to previous claims (12), arginine chelates with copper are not the only catalytically active species. For example, copper chelates with histidine and histamine are also active. The rates appear to be a first power function of copper and H202. Studies now being carried out with V. S. Sharma in our laboratories indicate that the active species is the Cu (II) L form where L represents the ligand. The copper chelate forms a ternary complex with... [Pg.494]

The most effective catalysts were found to be the 1 1 copper complexes with a,a -dipyridyl, L-histidine, o-phenanthroline, imidazole, and ethylene-diamine. Because of the apparent requirement that the metal be incompletely coordinated, it was suggested that the reactive positions of the metal are those occupied by water or hydroxide ion. Three such species have been reported by Fowkes et al. (9) from a study of aqueous equilibria involving the 1 1 dipyridyl chelate, according to the following reaction scheme ... [Pg.324]

Food products contain less copper than iron copper is mainly bound to protein as in ceruloplasmin. Copper ions are also chelated by albumin in mammalian and avian skeletal muscles and brain, they are chelated by camosine, anserine, and other histidine dipeptides. Cu + ions are more reactive than Fe ions and decompose hydrogen peroxide to produce hydroxyl radicals at a rate over 50 times higher than Fe + (Decker, 2001). However, the mechanism of the prooxidative effects of copper is most likely a mechanism other than that for iron, which is the reason why prevention of that catalysis in food systems requires a different strategy (Hultin, 1994). [Pg.147]


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See also in sourсe #XX -- [ Pg.178 , Pg.179 ]




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