Induction of phytoalexin synthesis in soybean: enzymatic cyclization of prenylated pterocarpans to glyceollin isomers.
A microsome preparation from elicitor-challenged soybean cell suspension cultures catalyzed an NADPH-dependent and oxygen-dependent cyclization of a mixture of 2- and 4-dimethylallylglycinols to the glyceollin isomers I-III. This is the last committed step in glyceollin biosynthesis. The cyclase was inhibited in a light-reversible manner by carbon monoxide in the presence of oxygen. Cyclase was also inhibited by cytochrome c, NADP+, and a number of inhibitors of cytochrome P-450 enzymes. NADH in the presence of low concentrations of NADPH had a synergistic effect. On a Percoll gradient, the position of cyclase coincided with marker enzymes for the endoplasmic reticulum. These properties identify the cyclase as a cytochrome P-450-dependent monooxygenase. Unstimulated soybean cell culture did not contain detectable cyclase activity. Challenge with either a glucan elicitor from Phytophthora megasperma f.sp. glycinea or with yeast extract caused strong stimulation of cyclase activity with a maximum at about 24 h after elicitor addition.
Welle
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Lehrstuhl für Biochemie der Pflanzen am Biologischen Institut II, Freiburg, Federal Republic of Germany.
Grisebach
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H
D001578:Benzopyrans / Q000378:metabolism*; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004122:Dimethylallyltranstransferase / Q000378:metabolism; D007536:Isomerism; D008861:Microsomes / Q000201:enzymology; D009249:NADP / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010936:Plant Extracts / Q000096:biosynthesis* / Q000378:metabolism; D010944:Plants / Q000201:enzymology*; D036343:Pterocarpans; D012717:Sesquiterpenes; D013729:Terpenes; D000094162:Phytoalexins
D001578:Benzopyrans; D010936:Plant Extracts; D036343:Pterocarpans; D012717:Sesquiterpenes; D013729:Terpenes; D009249:NADP; C017343:glyceollin; C042061:3,6,9-trihydroxypterocarpan; D004122:Dimethylallyltranstransferase; D010100:Oxygen; D000094162:Phytoalexins