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Fig. 3.12 RP-18 HPLC analysis of the enzymatic oxidation of tellimagrandin II ( 4 ) into
the dimeric ellagitannin cornusiin E ( 22 ) using an enzyme preparation from Tellima
grandiflora leaves. (―) complete enzyme assay; (····) control with acid-denatured
enzyme.
The cornusiin E ( 22 )-forming enzyme was also purified and
characterized. Its catalytic properties were found to be similar to the
tellimagrandin II ( 4 )-forming enzyme, but the molecular characteristics
of the two proteins were clearly different as shown by polyacrylamide
gel electrophoresis experiments (Niemetz and Gross, 2003b). The
reaction catalyzed by the enzyme is depicted in Fig. 3.13 to show how
the newly introduced 2,3'4'-valoneoyl bridge is formed by oxidative
intermolecular C-O coupling.
3.8 Conclusions and Perspectives
This chapter was written to demonstrate how efficiently extended
biochemical pathways can be elucidated by application of enzyme
studies, and also to show that such techniques can be easily practiced
even when using substrates as complex as hydrolyzable tannins. Besides
the presentation of scientific facts that had been gained in the past
decades, it would be satisfying if this article could have a positive impact
on present and future research by eliminating unfounded anxieties or
reservations to use such methods and experimental approaches.
Moreover, I hope — or better, I am confident — that the reported views
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