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Background:The details of the catalytic mechanism of cellobiose 2-epimerase (CE) remains unclear. Results: The crystal structures of Rhodothermus marinus CE in the apo form and complexes with its substrates/products 4-O-␤-D-glucopyranosyl-D-mannnose, epilactose, or cellobiitol (reaction intermediate analog) were elucidated. Conclusion: Epimerization catalyzed by CE proceeds through ring opening, deprotonation/reprotonation, carbon-carbon bond rotation, and ring closure. Significance: This study yielded structural insights into epimerization catalyzed by CE.

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The synthesis of JA-Ile was catalysed by JA-Ile synthase, which is a member of the group I GH3 family of proteins. Here, we showed evidence that OsGH3.5 (OsJAR1) and OsGH3.3 (OsJAR2) are the functional JA-Ile synthases in rice, using recombinant proteins. The expression levels of OsJAR1 and OsJAR2 were induced in response to wounding with the concomitant accumulation of JA-Ile. In contrast, only the expression of OsJAR1 was associated with the accumulation of JA-Ile after blast infection. Our data suggest that these two JA-Ile synthases are differentially involved in the activation of JA signalling in response to wounding and pathogen challenge in rice.