D-tagatose 3-epimerase

Bhuiyan et al.12531 immobilized i-rhamnose isomerase from Pseudomonas sp. LL172 on chitopearl beads, and used it to produce L-mannose from L-fructose. The immobilized enzyme was found to be stable it retained about 90% of the initial activity after five repeated batch reactions. The concentration of L-mannose relative to L-fructose was about 3 7 at equilibrium. D-Allose was also produced from d-psicose with the immobilized L-rhamnose isomerase. Since D-psicose is readily produced from D-fructose with D-tagatose 3-epimerase, D-allose can be produced from D-fructose by combination of the two enzymes immobilized on chitopearl beads. Bhuiyan et al. 254] found that the reaction progresses steadily until 40% of the D-psicose is converted into D-allose. The immobilized D-tagatose 3-epimerase was also stable even after repeated uses, and D-allose was produced efficiently in the system. 

Takeshita, K. et al.. Mass production of D-psicose from D-fructose by a continuous bioreactor system using immobilized D-tagatose 3-epimerase, J. Biosci. Bioeng., 90, 453, 2000. 

An investigation of the properties of the newly discovered l>ketose-3-epiinerase (see Vol. 27, Chapter 2, Ref S3) now named D-tagatose-3-epimerase, showed that it is most active on 3,4-cis configurated substrates, establishing a 30 70 cis/trans equilibrium. Thus the rare sugars D-sorbose and D-psicose have become available from >-tagatose and D-fhictose, respectively. ... 

Interesting extensions of isomerase chemistry are coupled enzyme systems. These could be advantageous for the removal of the desired isomer from the sometimes unfavourable equihbriiun to increase yields, as pointed out by Fess-ner and co-workers. Other apphcations could make rare sugars conveniently accessible from easily available starting materials, for example, in the preparation of D-psicose from o-fructose [6] by the combination of o-xylose isomerase with D-tagatose 3-epimerase. Clearly, the wide range of other available enzymes, for example, oxidoreductases, would allow for even more exciting opportunities to access unusual carbohydrates. 

D-Ketohexose-3-epimerase, a new enzyme isolated from Pseudomonas sp., catalysed the epimerization between D-tagatose and D-sorbose, D-fructose and D-psicose, D-xylulose and D-ribulose, and between L-xylulose and L-ribulose. ... 

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