Isolation and Characterization of a Mutant ofEscherichia coliBlocked in the Synthesis of Putrescine

Abstract

A mutant of Escherichia coli is described which is defective in the conversion of arginine to putrescine. The activity of the enzyme agmatine ureohydrolase is greatly reduced, whereas the activity of the other two enzymes of the pathway, the constitutive arginine decarboxylase and the inducible arginine decarboxylase, are within the normal range. The growth behavior of the mutant reflects the enzymatic block. It grows well in the absence of arginine, but only poorly in the presence of arginine. Under the former conditions, putrescine can be formed from ornithine as well as arginine, whereas under the latter conditions, because of feedback control, it can be formed only from arginine.

Regulation of Macromolecular Synthesis by Putrescine in a Conditional Escherichia coli Putrescine Auxotroph

“…When such filamentous cells are harvested and resuspended in fresh enriched media, either containing arginine (AFA) to continue putrescine starvation, or arginine and putrescine (AFAP) to relieve putrescine starvation, there is a dramatic difference between the growth rates of both cultures (14). Starved cells resuspended in AFA grow very slowly when either the absorbance at 580 nm or the actual viable count is measured.…”

“…Two different media were used to grow strain MA-135. The enriched medium (14), contained medium A (6) supplemented with 0.5% glucose and all amino acids (except arginine and ornithine), purines, pyrimidines, and vitamins, and was termed AF for arginine-free. When arginine (200 tsg/ml), ornithine (100 gg/ml), or arginine plus putrescine (100 gg/ml) was added, it was designated AFA, AFO, or AFAP, respectively.…”

“…Two methods were employed to deplete the supply of putrescine in the cell. The first involved starvation on AFA plates and has been described (14). These plate-starved cells were then used in all experiments requiring enriched media.…”

Properties of an Escherichia coli K-12 mutant defective in the transport of arginine and ornithine

“…Biosynthetic arginine decarboxylase, biodegradative (inducible) arginine decarboxylase, and agmatine ureahydrolase were measured by the methods of Hirshfield et al (17).…”

Metabolic pathway for the utilization of L-arginine, L-ornithine, agmatine, and putrescine as nitrogen sources in Escherichia coli K-12

“…L-Arginine decarboxylase (ADC; EC 4.1.1.19) and L-ornithine decarboxylase (ODC; EC 4.1.1.17) were assayed by the method of Tabor and Tabor (23). Agmatine ureohydrolase (AUH; EC 3.5.3.11) was assayed by the method of Hirshfield et al (10). Ornithine transaminase (OAT; EC 2.6.1.13) and putrescine transaminase (PAT; EC 2.6.1.16) were assayed by the method of Bilheimer et al (5).…”