Xanthine oxidase molecular weight

Professor Sabyasachi Sarkar (bom in 17 May 1947) is an Indian Chemist. He has explored chemistry passionately as a prospector to observe closely the clandestine activities of nature. He has worked and continued working in the diverse branches of chemistry closely related to natural set up and as such his research embraces functional models related to hyperthermophilic to mesophilic metalloproteins enriching bioinorganic chemistry. A Rephca of a Fishy Enzyme and the reduced xanthine oxidase also have been made. Inhibition patterns in the Michaelis complex of low molecular weight hepatic sulfite oxidase model complex have been exhibited. He demonstrated that carbon dioxide molecule does bind... 

It undergoes marked self-association and can be purified readily by chromatography on porous glass. The enzyme has a molecular weight of about 89 kDa, a pH optimum of 6.8-7.0, and a temperature optimum of 35°C. Its amino acid composition, its requirement for iron but not for molybdenum and FAD, and the catalytic properties of the enzyme, indicate that sulphydryl oxidase is a distinct enzyme from xanthine oxidase and thiol oxidase (EC 1.8.3.2). 

The inhibition of enzyme systems dues nut necessarily cause unwarned effects. Consider the enzyme xanthine oxidase. It contains two atoms of molybdenum, four Fe2S2, and two FAD (flavin adenine dinucleotidei moieties, and it has a molecular weight of 275.000-300.000. There is no evidence that the two units (Mo/SFe Sj/FAD) are near each other or interact in any way. It is believed that the immediate environment of each molybdenum atom consists of one oxygen and three sulfur atoms (additional ligands may be present) 12... 

Xanthine oxidase has a molecular weight of 300 000 and is dimeric. Each subunit contains one Mo, one FAD and one each of two types of Fe2S2 cluster. The Mov ESR signals are split by the iron-sulfur centre I, so allowing the calculation of distances between the two centres.1012 1014 The most recent estimate is close to 15 A, with a lower limit of 12 A, a value that holds also for aldehyde oxidase.1015... 

The question now arises as to why xanthine oxidase has a molecular weight of 300,000 when the size of a catalytic subunit is only 150,000. Perhaps the answer lies in its particular integration into cellular physiology or is simply caused by the proclivity of the enzyme to maximize the number of active sites per unit surface area i.e., when two active monomers join together, the number of active sites goes from one to two, but the exposed surface area increases by a factor less than two. This argument is a familiar one in heterogeneous catalysis where attempts are often made to maximize the number of active sites per unit surface area to produce more efficient catalysts. 

Ganelin et al. (11) provided evidence that the molybdenum cofactor is a molybdenum peptide with a molecular weight of about 1000. The same properties have been claimed for the cofactor from xanthine oxidase (12). 

Xanthine oxidase has been isolated from milk and obtained in the crystalline state. The molecular weight is 275,000. One mole of the protein contains 2 moles of FAD, 2 gram-atoms of molybdenum, 8 gram-atoms of nonheme iron, and 8 labile sulfide groups. The 8 labile sulfide groups are liberated in the form of H2S upon acidification or boiling at pH 7. The optimum pH for activity is 8.3. The xanthine oxidase in milk is associated with the fat globules and, therefore, follows the fat into the cream when milk is separated. It seems to be located in small particles (microsomes) that are attached to the fat... 

Small-molecular-weight copper complexes also inhibit lipid peroxidation. The oxidation of linolenic acid by the xanthine oxidase-acetaldehyde superoxide generating system was prevented by Cu(II)2(lonazolac)4 [194]. This eom-plex was also effective in inhibiting linolenic acid oxidation in the presence of... 

The specificity of this enzyme is low it will convert adenine to its 8-hydroxy and 2,8-dihydroxy derivatives and will also oxidize a wide variety of nonpurine substrates. Xanthine oxidase contains 2 moles of FAD, 2 moles of Mo(V), and 8 moles of Fe + its molecular weight is 200,000-... 

In order to test the applicability of the method tryptophan determinations were carried out on a number of proteins whose molecular weight and amino acid composition were known (29, 30, 73, 254). The resulting values are in close agreement with those given in the literature. The molar magnetic ellipticity per tryptophan residue of these proteins and model compounds has recently served to quantitate the tryptophan content of xanthine oxidase 32). 

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