Dissimilation of methionine in cell suspension cultures fromCatharanthus roseusL.

✍ Scribed by Jens D. Schwenn; Ulrich Schriek; Hans H. Kiltz

• Publisher: Springer-Verlag
• Year: 1983
• Tongue: English
• Weight: 1003 KB
• Volume: 158
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00397245

✦ Synopsis

Plant cell suspension cultures from Catharanthus roseus were investigated for their capability to dissimilate methionine or its analogs in order to reutilize the sulphane group for cysteine biosynthesis. Three steps have been described as prerequisites of this process: (a) oxidative degradation by the amino-acid oxidase of methionine giving rise to methanethiol production; (b) demethylation by methyltransferases leading to homocysteine and Smethylmethionine; (c) replacement of the homocysteine sulphane sulphur by alkylthiol yielding methionine and free hydrogen sulphide. A reversal of the cystathi0nine pathway as a source of cysteine was ruled out because the cells lack cystathionine ?-lyase. The absence of this enzyme is compensated by the S-alkyl exchange of homocysteine with methylmercaptan. Hydrogen sulphide thus liberated is used for de novo synthesis of cysteine. The complete pathway can be catalyzed by the constitutive set of enzymes present in the higher plant.