Reconstitution of a bacterial/plant polyamine biosynthesis pathway in Saccharomyces cerevisiae

Polyamine synthesis in most organisms is initiated by the decarboxylation o f ornithine to form putrescine via ornithine decarboxylase (ODC), Plants, s ome bacteria and some fungi and protozoa generate putrescine from arginine, via arginine decarboxylase (ADC) and agmatine ureohydrolase (AUH) or agmat ine iminohydrolase. A polyamine-requiring strain of Saccharomyces cerevisia e with a mutation in the gene encoding ODC was transformed with plasmids be aring genes encoding Escherichia coli ADC and AUH. Transformants regained t he ability to grow in the absence of exogenous polyamines and contained enz yme activities consistent with the presence of both prokaryotic enzymes. Si milar results were obtained when a plasmid containing a gene encoding oat ( Avena sativa L.) ADC was substituted for the E. coli gene. These data demon strate the successful complementation of a yeast biosynthetic polyamine syn thesis defect by genes encoding an alternative pathway found in bacteria; t hey also show that plant ADC can substitute for the bacterial enzyme in thi s pathway. The recombinant yeast provides a tool for the study of the funct ional properties of these enzymes and for discovery of compounds that speci fically inhibit this pathway.