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Escherichia coli K-12 mutants that carry deletions in their genes for ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) (speC), arginine decarboxylase (L-arginine carboxy-lyase, EC 4.1.1.19) (speA), and agmatine ureohydrolase (agmatinase or agmatine amidinohydrolase, EC 3.5.3.11) (speB) can still synthesize very small amounts of putrescine and spermidine. The putrescine concentration in these mutants was found to be 1/2500th that in spe+ cells. The pathway of putrescine synthesis appears to be through the biodegradative arginine decarboxylase, which converts arginine to agmatine, in combination with a low agmatine ureohydrolase activity--1/2000th that in spe+ strains. These results suggest that even such low levels of polyamines permit a low level of protein synthesis. Evidence is presented that the polyamine requirement for the growth of the polyamine-dependent speAB, speC deletion mutants, which are also streptomycin resistant, is not due to a decreased ability to synthesize polyamines.

proceedings of the national academy of sciences of the united states of america

Biosynthesis of polyamines in ornithine decarboxylase, arginine decarboxylase, and agmatine ureohydrolase deletion mutants of Escherichia coli strain K-12.