tailieunhanh - Báo cáo khoa học: Novel type III polyketide synthases from Aloe arborescens

Aloe arborescensis a medicinal plant rich in aromatic polyketides, such as pharmaceutically important aloenin (hexaketide), aloesin (heptaketide) and barbaloin (octaketide). Three novel type III polyketide synthases (PKS3, PKS4 and PKS5) were cloned and sequenced from the aloe plant by cDNA library screening. | ỊFEBS Journal Novel type III polyketide synthases from Aloe arborescens Yuusuke Mizuuchi1 She-Po Shi1 Kiyofumi Wanibuchi1 Akiko Kojima1 Hiroyuki Morita1 Hiroshi Noguchi1 and Ikuro Abe1 2 1 Schoolof PharmaceuticalSciences University of Shizuoka Japan 2 PRESTO Japan Science and Technology Agency Kawaguchi Saitama Japan Keywords Aloe arborescens aloenin aloesin aloesone synthase type III polyketide synthase Correspondence I. Abe University of Shizuoka 52-1 Yada Shizuoka 422-8526 Japan Fax Tel 81 54 264 5662 E-mail abei@ Note The nucleotide sequences have been deposited in the EMBL DDBJ GenBank databases under accession numbers EF537574 FJ536166 and FJ536167 Received 29 December 2008 revised 2 February 2009 accepted 17 February 2009 doi Aloe arborescens is a medicinal plant rich in aromatic polyketides such as pharmaceutically important aloenin hexaketide aloesin heptaketide and barbaloin octaketide . Three novel type III polyketide synthases PKS3 PKS4 and PKS5 were cloned and sequenced from the aloe plant by cDNA library screening. The enzymes share 85-96 amino acid sequence identity with the previously reported pentaketide chromone synthase and octaketide synthase. Recombinant PKS4 and PKS5 expressed in Escherichia coli were functionally identical to octaketide synthase catalyzing the sequential condensations of eight molecules of malonyl-CoA to produce octaketides SEK4 SEK4b. As in the case of octaketide synthase the enzymes are possibly involved in the biosynthesis of the octaketide barbaloin. On the other hand PKS3 is a multifunctional enzyme that produces a heptaketide aloesone . the aglycone of aloesin as a major product from seven molecules of malonyl-CoA. In addition PKS3 also afforded a hexaketide pyrone . the precursor of aloenin a heptaketide 6- 2-acetyl-3 5-dihydroxybenzyl -4-hydroxy-2-pyrone a novel heptaketide 6- 2- 2 4-dihydroxy-6-methylphe-nyl -2-oxoethyl -4-hydroxy-2-pyrone and octaketides .