Benzalacetone synthase

ABE, I., TAKAHASHI, Y., MORITA, H., NOGUCHI, H., Benzalacetone synthase a novel polyketide synthase that plays a crucial role in the biosynthesis of phenylbutanones in Rheum palmatum, Eur. J. Biochem., 2001,268, 3354-3359. 

Fig. 1 Biosynthesis of plant polyphenols by CHS-superfamily type III PKSs. CHS chalcone synthase STS stilbene synthase ACS acridone synthase VPS valerophenone synthase SPS styrylpyrone synthase BPS benzophenone synthase OAS olivetolic acid synthase 2PS 2-pyrone synthase BAS benzalacetone synthase CUS curcumin synthase...

Abe I, Sano Y, Takahashi Y, Noguchi H (2003) Site-directed mutagenesis of benzalacetone synthase the role of Phe215 in plant type III polyketide synthases. J Biol Chem 278 25218-25226... 

Abe T, Morita H, Noma H, Kohno T, Noguchi H, Abe I (2007) Structure function analysis of benzalacetone synthase from Rheum palmatum. Bioorg Med Chem Lett 17 3161-3166... 

Raspberries accumulate a variety of flavonoid and aroma compounds that derive from PKS type III reactions (Borejsza-Wysocki and Hrazdina, 1996, Zheng et al., 2001). CHS produces precursors for flavonol, flavandiol and anthocyanin synthesis. Benzalacetone synthase (BAS) carries out a single condensation step in the synthesis of p-hydroxybenzalacetone, the precursor of raspberry ketone, that is responsible for the characteristic aroma of raspberries. To understand the role of the type III PKS during the ripening of fruits, we cloned and characterized five type III PKS genes/gene products and discuss then-properties below. 

Further analysis of the raspberry PKS genes has shown that the proteins coded by the five genes have the seven conserved cysteines at positions 30,60,84,130,164,190 and 341. Cysteines at these conserved locations are likely to have structural functions, because in addition to the CHS from which the consensus sequence derives, they were found at identical or similar locations in Arachis hypogea STS, in the Gerbera hybrida 2-pyrone synthase (2PS), in the Ruta graveolens acridone synthase (ACS), the Rheum palmatum benzalacetone synthase (BAS) and in the aleosone synthase (ALS) (Abe et al., 2004). 

Morita H, Tanio M, Kondo S, Kato R, Wanibuchi K, Noguchi H, Sugio S, Abe I, Kohno T (2008) Crystallization and preliminary crystallographic analysis of a plant type III polyketide synthase that produces benzalacetone. Acta Crystallograph Sect F Struct Biol Cryst Commun 64 304-306... 

---