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Figure 4.
Figure 4: Comparison of Diels -Alderases. a, Solanapyrone
synthase (SPS) catalyses oxidation of alcohol 7 to the reactive
formyl derivative which readily promotes [4 + 2] cycloaddition
to give solanapyrone A 8. b, Lovastatin nonaketide synthase
(LNKS) catalyses intramolecular [4 + 2] cycloaddition from 9 to
10. LNKS also catalyses condensation of acetyl CoA and malonyl
CoA to form an enzyme bound analogue of 9. SNAC is
N-acetylcysteamine thioester. c, Diels -Alderase antibody 1E9
transforms thiophene dioxide 11 and maleimide 12 to intermediate
13 via [4 + 2] cycloaddition, which is then converted into
aromatic product 14 with elimination of sulphur dioxide and the
subsequent oxidation. Non-catalysed degradation from 13 to 14
allows this catalytic antibody to escape the product inhibition.
This leads 1E9 to be the most efficient Diels -Alderase antibody.
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