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Metabolism and Enzymology

Hydroxycinnamoyl-CoA:Putrescine Hydroxycinnamoyltransferase in Tobacco Cell Cultures with High and Low Levels of Caffeoylputrescine ¹

Botanisches Institut der Universität Köln, D-5000 Köln 41, Federal Republic of Germany, GBF-Gesellschaft für Biotechnologische Forschung m.b.h., Mascheroder Weg 1, D-3300 Braunschweig, Federal Republic of Germany

A new hydroxycinnamoyl-CoA:putrescine hydroxycinnamoyltransferase (PHT) was detected in two variant lines of Nicotiana tabacum L. (TX1, TX4) accumulating markedly different levels of caffeoylputrescine. The enzyme accepted only the aliphatic diamines putrescine, cadaverine and 1,3-diaminopropane at a ratio of 100:33:8. Caffeoyl- and feruloyl-CoAs were the best acyl donors. The apparent K_m-values for caffeoyl-CoA and putrescine were near 3 and 10 micromolar, respectively, at the pH-optimum of 10.0. PHT activity was quite similar in low producing TX1 and high producing TX4 cells, while some other biosynthetic enzymes (phenylalanine ammonia-lyase, ornithine decarboxylase) were greatly enhanced in TX4 cells, suggesting that PHT does not catalyze the rate-limiting step in hydroxycinnamoylputrescine formation.

³ Present address: Institut für Pharmazeutische Biologie der Technischen Universität, D-3300 Braunschweig, FRG.

¹ Supported by Deutsche Forschungsgemeinschaft.