Identification and characterization of a novel sesquiterpene synthase from Aquilaria sinensis: An important gene for agarwood formation.

Sesquiterpene synthases are key enzymes for biosynthesis of sesquiterpene compounds and are important for agarwood formation in Aquilaria sinensis.The As-sesTPS gene encoding a novel sesquiterpene synthase was expressed in Escherichia coli strain BL21 (DE3) as an inclusion body and purified by Ni affinity chromatography. The molecular weight of the protein was lower than the theoretical value. Amino acid sequencing results indicated that the 27.2kDa-recombinant protein was a truncated sesquiterpene synthase from chemically induced A. sinensis. After refolding, the truncated As-SesTPS protein catalyzed the conversion of farnesyl pyrophosphate (FPP) to nerolidol which is a characteristic component of agarwood. The optimal reaction pH for the As-SesTPS protein was 8.0, and the optimal temperature was 30°C. The values of Km and Vmax of As-SesTPS protein towards FPP were 0.0548mM, 42.83μmol/mg.min, respectively. The results of qPCR and iTRAQ demonstrated the much higher expression level of As-SesTPS gene in agarwood than that in whitewood. This study provides a foundation for elucidating the mechanism of agarwood formation in A. sinensis and the potential of the novel gene for improving the quality of artificial agarwood.