Enzymatic formation of long-chain polyketide pyrones by plant type III polyketide synthases.
Recombinant chalcone synthase (CHS) from Scutellaria baicalensis and stilbene synthase (STS) from Arachis hypogaea accepted CoA esters of long-chain fatty acid (CHS up to the C12 ester, while STS up to the C14 ester) as a starter substrate, and carried out sequential condensations with malonyl-CoA, leading to formation of triketide and tetraketide alpha-pyrones. Interestingly, the C6, C8, and C10 esters were kinetically favored by the enzymes over the physiological starter substrate; the kcat/KM values were 1.2- to 1.9-fold higher than that of p-coumaroyl-CoA. The catalytic diversities of the enzymes provided further mechanistic insights into the type III PKS reactions, and suggested involvement of the CHS-superfamily enzymes in the biosynthesis of long-chain alkyl polyphenols such as urushiol and ginkgolic acid in plants.
Abe
Ikuro
I
School of Pharmaceutical Sciences and the 21st Century COE Program, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. abei@ys7.u-shizuoka-ken.ac.jp
Watanabe
Tatsuya
T
Noguchi
Hiroshi
H
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000217:Acyltransferases / Q000737:chemistry / Q000378:metabolism*; D010367:Arachis / Q000201:enzymology*; D001665:Binding Sites; D007700:Kinetics; D015394:Molecular Structure; D011753:Pyrones / Q000378:metabolism*; D031363:Scutellaria / Q000201:enzymology*
D000214:Acyl Coenzyme A; D011753:Pyrones; C058644:4-coumaroyl-coenzyme A; D000217:Acyltransferases; C022674:stilbene synthase; C020141:flavanone synthetase