ISSN:
1432-0797
Source:
Springer Online Journal Archives 1860-2000
Topics:
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract The interactions of Mn2+ and Co2+ with glucose isomerases from three microbial sources have been studied using various direct physical methods. Co2+ was found to activate each enzyme, although the degree of activation varied significantly for enzymes from different organisms. EPR spectroscopy measurements revealed that dissimilarities in the coordination sphere of enzyme-bound Mn2+ accompanied the differences in enzyme activity. Variations in the EPR spectra of a nitroxide spin label coupled to two of the three isomerases, possibly near their active sites, were also observed. In no case was the EPR spectrum influenced by Co2+ addition, a result discordant with the hypothesis that Co2+ activates the enzyme by inducing a conformational change. The proximal biochemical environment of enzymebound Co2+ was also examined using EXAFS spectroscopy. This method showed that glucose causes notable changes in the ligand environment of the enzyme-bound metal, suggesting the formation of an enzyme-metal-substrate bridge complex. The significance of these results relative to possible reaction mechanisms is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00387498
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