Formation of benzoquinol moiety in cornoside by salidroside mono-oxygenase, a cytochrome P450 enzyme, from Abeliophyllum distichum cell suspension cultures

• Published in: Planta 2003-01, Vol.216 (3), p.432-436
• Main Authors: Yamamoto, Hirobumi, Hori, Mitsuko, Kuwajima, Hiroshi, Inoue, Kenichiro
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Cell culture techniques; Cultured cells; Cytochrome; Cytochromes; Economic plant physiology; Enzymes; Fundamental and applied biological sciences. Psychology; Glucosides; Hydroquinones; Metabolism; Nutrition. Photosynthesis. Respiration. Metabolism; Oxidases; Oxidation; Phenols; Plant physiology and development; Plants
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-002-0896-0

A microsomal fraction prepared from Abeliophyllum distichum Nakai (Oleaceae) cell suspension cultures oxidized salidroside, a glucoside of 4-hydroxyphenylethyl alcohol, to cornoside possessing a unique benzoquinol ring. The enzyme named salidroside mono-oxygenase required NADPH as the only cofactor, and molecular oxygen. The reaction was strongly inhibited by CO as well as several cytochrome P450 inhibitors, such as cytochrome c and miconazole, indicating the involvement of a cytochrome P450 enzyme. Salidroside mono-oxygenase accepted salidroside as the only substrate, but did not oxidize 4-hydroxyphenylethyl alcohol, the salidroside aglucone, and 4-hydroxybenzoic acid. The optimum pH of the reaction was 7.5, and apparent Km values for salidroside and NADPH were 44 μM and 33 μM, respectively. The benzoquinol ring formation mechanism is discussed in comparison to the mechanism for ipso substitution of 4-hydroxybenzoate by active oxygen species followed by elimination leading to hydroquinone.