Abstract
We report that entrapping glucose oxidase (GOx) within metallic gold, expands its activity to become an oxidase for monosaccharides that do not have a natural enzyme with that activity—fructose and xylose—and that this entrapment also removes the enantioselectivity, rendering this enzyme capable of oxidizing the “wrong” l-enantiomer of glucose. These observations suggest that in this biomaterial adsorptive interactions of the outer regions of the protein with the gold cage, pull apart and widen the tunnel between the two monomeric units of GOx, to a degree that its stereoselectivity is compromised; then, the active sites which are more versatile than currently attributed to, are free and capable of acting on the foreign sugars. To test this proposition, we entrapped in gold l-asparaginase, which is also a dimeric enzyme (a dimer of tight dimers), and found, again, that this metallic biomaterial widens the activity of that enzyme, to include the D-amino acid counter enantiomer as well. Detailed kinetic analyses for all substrates are provided for the gold bio-composites, including determination of the difference between the activation energies towards two opposite enantiomers.
Highlights
We report that entrapping glucose oxidase (GOx) within metallic gold, expands its activity to become an oxidase for monosaccharides that do not have a natural enzyme with that activity—fructose and xylose—and that this entrapment removes the enantioselectivity, rendering this enzyme capable of oxidizing the “wrong” l-enantiomer of glucose
In biochemistry but in chemistry at large, the opposite extreme is of central use: catalysts and reagents which have a broad, general spectrum of activity. In biochemistry this direction has focused on the following question: How can one generalize the activity of an enzyme beyond its evolutionary developed specific mode of action7–9? The importance of that branch of research is already displayed in the title of this report: Glucose oxidase (GOx) is a very common, useful, low-cost enzyme of the EC 1.1.3 oxidoreductases family which utilizes oxygen for oxidation of specific CH-OH groups in various saccharides
We report that entrapment of GOx within metallic gold, expands its oxidase activity to diverse monosaccharides which include, as already mentioned above, another hexose–fructose, a pentose–xylose and the counter enantiomer l-glucose
Summary
We report that entrapping glucose oxidase (GOx) within metallic gold, expands its activity to become an oxidase for monosaccharides that do not have a natural enzyme with that activity—fructose and xylose—and that this entrapment removes the enantioselectivity, rendering this enzyme capable of oxidizing the “wrong” l-enantiomer of glucose. We report that entrapment of GOx within metallic gold, expands its oxidase activity to diverse monosaccharides which include, as already mentioned above, another hexose–fructose, a pentose–xylose and the counter enantiomer l-glucose.
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