Metalloproteins/Metalloenzymes

It is well known that a great variety of biomolecules exist where metals and metalloids are bound to proteins and peptides, coordinated by nucleic acids or complexed by polysaccharides and small organic ligands such as organic acids.55 Most proteins contain amino acids with covalently bonded heteroelements such as sulphur, selenium, phosphorus or iodine.51 Several reviews have been published on the development of mass spectrometric techniques for bioanalysis in metal-lomics , which integrate work on metalloproteins, metalloenzymes and other metal containing biomolecules.1 51 53 54 56-59 The authors consider trace metals, metalloids, P and S (so-called... 

In the 2002 international symposium on bio-trace elements held in Japan, Haraguchi proposed the concept and term of metallomics as a new scientific field to integrate the research fields related to biometals. The concept was further elucidated in his successive publication, in which metallomics was defined as bio-trace element science, and metalloproteins, metalloenzymes and other metal-containing biomolecules were defined as metallomes in a similar manner to genomes in genomics as well as proteomes in proteomics. Subsequently, the term metallomics has been used as the name for the study of metallomes. Szpunar defined metallomics as ... comprehensive analysis of the entirety of metal and metalloid species within a cell or tissue type . ... 

METALLOPROTEINS. Metalloproteins are either metal storage forms, as in the case of ferritin, or enzymes in which the metal atom participates in a catalyti-cally important manner. We encounter many examples throughout this book of the vital metabolic functions served by metalloenzymes. 

Cohen lA (1980) Metal-Metal Interactions in the Metalloporphyrins, Metalloproteins and Metalloenzymes. 40 1-37... 

Volume 226. Metallobiochemistry (Part C Spectroscopic and Physical Methods for Probing Metal Ion Environments in Metalloenzymes and Metalloproteins) Edited by James F. Riordan and Bert L. Vallee... 

The ionization is the rds. The spontaneous rate is considered to be accelerated by both inter-molecular (from the buffer) and intramolecular (from His-64) proton transfer. Cadmium can replace the native zinc from metalloenzymes and Cd nmr is being used increasingly to probe metal ligation sites in metalloproteins. The cadmium product often does not show enzyme activity however. 

Electron nuclear double resonance (ENDOR) and electron spin-echo envelope modulation (ESEEM) are two of a variety of pulsed EPR techniques that are used to study paramagnetic metal centers in metalloenzymes. The techniques are discussed in Chapter 4 of reference la and will not be discussed in any detail here. The techniques can define electron-nuclear hyperfine interactions too small to be resolved within the natural width of the EPR line. For instance, as a paramagnetic transition metal center in a metalloprotein interacts with magnetic nuclei such as H, H, P, or these... 

Copper Metalloenzymes and Metalloprotein The copper enzymes are mostly oxidases, that is enzymes which catalyse oxidations. Examples are ... 

It is not sufficient to show that the active protein contains zinc, in order to classify the enzyme to be a metalloenzyme. It must be proved that the zinc in the metalloprotein is functional. This point was examined27 with preparations similar to the final products listed in Table IX. Although the enzyme was completely resistant to the action of EDTA at pH 8 (see Table VI p. 414), the preparations were still inactivated by the chelating agent at pH 5. Activity was restored by Zn2+, but by no other cation examined. 

Zinc in metalloenzymes may (i) participate directly in the catalytic process, (ii) serve to stabilize protein structure or (iii) have a regulatory role. In each case, removal of the metal from the holoenzyme generally results in an apoprotein having no catalytic activity. The enzymes considered briefly below provide examples of each of these functions of Zn. The study of zinc metalloproteins has often in the past been beset by analytical problems and by contamination with traces of metal ions a review covering these important topics has appeared.1263 Another recent review deals with the physiological, nutritional and medical role of zinc.1264... 

---