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Publication Abstract from PubMed

Terpene synthases (TS) are classified into two broad types, Class I and II, based on the chemical strategy for initial carbocation formation and motif sequences of the catalytic site. We have recently identified a new class of enzymes, Class IB, showing the acceptability of long (C20-C35) prenyl-diphosphates as substrates and no amino acid sequence homology with known TS. Conversion of long prenyl-diphosphates such as heptaprenyl-diphosphate (C35) is unusual and has never been reported for Class I and II enzymes. Therefore, the characterization of Class IB enzymes is crucial to understand the reaction mechanism of the extensive terpene synthesis. Here, we report the crystal structure bound with a substrate surrogate and biochemical analysis of a Class IB TS, using the enzyme from Bacillus alcalophilus (BalTS). The structure analysis revealed that the diphosphate part of the substrate is located around the two characteristic Asp-rich motifs, and the hydrophobic tail is accommodated in a unique hydrophobic long tunnel, where the C35 prenyl-diphosphate, the longest substrate of BalTS, can be accepted. Biochemical analyses of BalTS showed that the enzymatic property, such as Mg(2+) dependency, is similar to those of Class I enzymes. In addition, a new cyclic terpene was identified from BalTS reaction products. Mutational analysis revealed that five of the six Asp residues in the Asp-rich motifs and two His residues are essential for the formation of the cyclic skeleton. These results provided a clue to consider the application of the unusual large terpene synthesis by Class IB enzymes.

Characterization of Class IB Terpene Synthase: The First Crystal Structure Bound with a Substrate Surrogate.,Stepanova R, Inagi H, Sugawara K, Asada K, Nishi T, Ueda D, Yasuno Y, Shinada T, Miki K, Fujihashi M, Sato T ACS Chem Biol. 2020 Jun 19;15(6):1517-1525. doi: 10.1021/acschembio.0c00145. Epub, 2020 Apr 13. PMID:32227910^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.