Acridone synthase

JUNGHANNS, K.T., KNEUSEL, R.E., BAUMERT, A, MAIER, W GROGER, D., MATERN, U., Molecular cloning and heterologous expression of acridone synthase from elicited Ruta graveolens L cell suspension cultures, Plant Molec. Biol., 1995, 27, 681-692. 

LUKACIN, R., SPRINGOB, K., URBANKE, C., ERNWEIN, C., SCHRODER, G., SCHRODER, J., MATERN, U., Native acridone synthases I and H from Ruta graveolens L. form homodimers, FEBSLett., 1999,448,135-140. 

Acridone alkaloids Acridone synthase Ruta graveolens... 

PKSs are characterized by their ability to catalyze the formation of polyketide chains from the sequential condensation of acetate units from malonate thioesters. In plants they produce a range of natural products with varied in vivo and pharmacological properties. PKSs of particular note include acridone synthase, bibenzyl synthase, 2-pyrone synthase, and stilbene synthase (STS). STS forms resveratrol, a plant defense compound of much interest with regard to human health. STS shares high sequence identity with CHS, and is considered to have evolved from CHS more than once. ° Knowledge of the molecular structure of the CHS-like enzymes has allowed direct engineering of CHS and STS to alter their catalytic activities, including the number of condensations carried out (reviewed in Refs. 46, 51, 52). These reviews also present extensive, and superbly illustrated, discussions of CHS enzyme structure and reaction mechanism. 

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...

Lukacin R, Springob K, Urbanke C, Emwein C, Schroder G, Schroder J, Matem U (1999) Native acridone synthases I and II from Rura graveolens L. form homodimers. FEBS Lett 448 135-140... 

Baumert, A., Maier, W., Groger, D. and Deutzmarm, R. (1994) Purification and properties of acridone synthase from cell suspension cultures of Ruta graveolens (L.). Z. Naturforsch., 49c, 26-32. 

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). 

Biosynthesis From IV-methylanthraniloyl-CoA and 3 mol. malonyl-CoAthe acridone synthase exhibits a high sequence homology with a synthase of the chal-cones. ... 

An acridone synthase respraisible for the conversion of Af-methylanthraniloyl CoA and malonyl CoA into l,3-d3iydroxy-Af-methylacridone (33, Scheme 24.10) has been purified from cell suspensimi cultures of Ruta graveolens and characterized [115,116]. The essential Af-methylatiOTi of the starter substrate was supported also by the anthrani-late Af-methyhransferase activity detected in crude extracts of R. graveolens cells [117]. 

Fig. 2 Reaction types catalyzed by plant type III polyketide synthases. PS, pyrone synthase CHS, chalcone synthase STS, stilbene synthase VPS, valerophenone synthase ACS, acridone synthase BPS, benzophe-none synthase...

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