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The evolution of sugar isomerases
S Banerjee1, F Anderson, G K Farber
1Department of Biochemistry and Molecular Biology, Pennsylvania State Universi University Park 16802, USA.
Protein Engineering
|December 1, 1995
Summary
L-arabinose isomerase from E. coli uses a proton transfer mechanism, unlike xylose isomerase. This enzyme requires Manganese(II) for activity and shows high substrate specificity for L-arabinose.
Area of Science:
- Enzymology
- Biochemistry
- Protein Mechanisms
Background:
- L-arabinose isomerase (EC 5.3.1.4) catalyzes the conversion of L-arabinose to L-ribulose.
- Understanding enzyme mechanisms is crucial for biochemistry and biotechnology.
Purpose of the Study:
- To elucidate the purification, kinetic mechanism, and chemical mechanism of L-arabinose isomerase from Escherichia coli.
- To compare the catalytic mechanism with that of xylose isomerase.
Main Methods:
- Enzyme purification from Escherichia coli.
- Kinetic analysis to determine reaction rates and dependencies.
- Chemical mechanism investigation using biochemical assays.
Main Results:
- L-arabinose isomerase was purified from E. coli.
- The enzyme catalyzes isomerization via a proton transfer mechanism, distinct from xylose isomerase's hydride transfer.
- Activity is dependent on Manganese(II), with high substrate specificity for L-arabinose.
Conclusions:
- The distinct mechanisms suggest L-arabinose isomerase and xylose isomerase are not related by convergent evolution.
- Enzyme mechanisms should not be assumed to be similar for enzymes catalyzing the same reaction without demonstrated convergent evolution.