Porphyrin and Heme Biosynthesis from Endogenous and Exogenous δ-Aminolevulinic Acid inEscherichia coli, Pseudomonas aeruginosa,andAchromobacter metalcaligenes

Abstract

Porphyrin and heme synthesis from endogenous and exogenous -aminolevulinic acid in Pseudomonas aeruginosa, Escherichia coli, and Achromobacter metalcaligenes was studied in growing cultures and in resuspended cells under moderately aerobic conditions. Similar investigations were also performed on A. metalcaligenes during the entire course of growth. Lactate served as the only source of energy for the growing and the resuspended cells; there was no supplementation with iron. Each of the three microorganisms synthesized from lactate all porphyrins with 8 to 2 carboxylic acid side chains, corresponding to the biosynthetic sequence. The relative amounts of porphyrins formed by Ps. aeruginosa, E. coli, and A. metalcaligenes are 5:1:1, and of heme 1:1.8:2.4. With exogenous -aminolevulinic acid theaminolevulinate synthase is bypassed, thus eliminating the latter's function as a regulatory ratelimiting enzyme. From lactate and ammonium

TolC-Dependent Exclusion of Porphyrins in Escherichia coli

“…This is probably the reason why mainly coproporphyrin(ogen) was accumulated in the ALA-treated cells. These findings match well with previous observations (10,27). The function of the TolC-dependent efflux system may be to prevent the intracellular accumulation of excess porphyrin(ogen)s when cells are exposed to high concentrations of ALA.…”

“…Accumulation of porphyrin(ogen)s in tolC mutant cells. We extracted intracellular porphyrin(ogen)s from the wild-type and tolC mutant cells grown in the presence of 10 g/ml ALA. Porphyrinogens, if present, would have been oxidized during the extraction procedures; therefore, the extracted samples should have contained porphyrins (10,27). The total porphyrin concentrations were determined by fluorescence spectrometry with an excitation wavelength of 405 nm.…”

“…In the 1970s, Doss and Philippe-Dormston demonstrated that exogenous ALA stimulates porphyrin biosynthesis in several bacteria, including E. coli (10,27). They also showed that the synthesized porphyrin(ogen)s then are exported into the medium.…”

Co-ordination of iron acquisition, iron porphyrin chelation and iron–protoporphyrin export via the cytochrome c biogenesis protein CcmC in Pseudomonas fluorescens

“…2a). As expected, and in agreement with earlier observations for various other bacteria, the wild-type and mutant strains grown in the absence of ALA did not contain significantly overproduced tetrapyrroles (Doss & Philipp-Dornston, 1971;Philipp-Dornston & Doss, 1973).…”

“…Porphyrinogens and porphyrins accumulated by the ccmC mutant grown in the presence and absence of ALA were determined by HPLC analysis. ALA was added to growth media to overcome the initial rate-limiting step of tetrapyrrole biosynthesis and to allow significant detectable tetrapyrrole accumulation (Doss & Philipp-Dornston, 1971;Philipp-Dornston & Doss, 1973). The data presented in Fig.…”