2,6-Pyridinedicarbothioic acid explained

2,6-Pyridinedicarbothioic acid (PDTC) is an organosulfur compound that is produced by some bacteria. It functions as a, a low molecular weight compound that scavenges iron. Siderophores solubilize compounds by forming strong complexes. PDTC is secreted by the soil bacteria Pseudomonas stutzeri and Pseudomonas putida.^[1]

Synthesis and biosynthesis

PDTC can be synthesized in the laboratory by treating the diacid dichloride of pyridine-2,6-dicarboxylic with H₂S in pyridine:

This route produces the pyridinium salt of pyridinium-2,6-dicarbothioate. Treatment of this orange-colored salt with sulfuric acid gives colorless PDTC, which can then be extracted with dichloromethane.^[2]

The biosynthesis of PDTC remains unclear although some insights can be deduced from the genetics.^[3] It is suggested that Pseudomonas stutzeri may have acquired at least one of the genes by lateral transfer from mycobacteria.^[4] In a proposed biosynthetic sequence pyridine-2,6-dicarboxylic acid, a known bacterial metabolite,^[4] is activated as its bis-adenosine monophosphate (AMP) derivative. The sulfur donor and its activation remain uncertain.^[5]

Coordination chemistry

PDTC binds to both Fe²⁺ and Fe³⁺. The ferric complex is brown, whereas the ferrous complex is blue. In the presence of air, the ferrous complex oxidizes to the ferric compound.^[6] It is iron selective^[4] as only the Fe complex is soluble in water. PDTC is produced mainly during the exponential phase of bacterial growth. The conditions at which Pseudomonas produces PDTC is 25 °C, pH=8 and sufficient aeration.^[5]

See also

• Dipicolinic acid

Notes and References

1. Book: Budzikiewicz, Herbert . 10.1007/978-3-211-99661-4_1 . 2010 . Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products, Vol. 92 . A. Douglas . Kinghorn . Heinz . Falk . Junichi . Kobayashi . 92 . Progress in the Chemistry of Organic Natural Products . Microbial Siderophores . 1–75 . 20198464 . 978-3-211-99660-7.
2. 10.1080/03086648308080490 . Zur Struktur Eines 1:1-Adduktes von Pyridin-2,6-Dicarbothiosäure und Pyridin . 1983 . Hildebrand . U. . Ockels . W. . Lex . J. . Budzikiewicz . H. . Phosphorus and Sulfur and the Related Elements . 16 . 3 . 361–364 .
3. 10.1186/1471-2148-2-8 . 2002 . Cortese . Marc S . Caplan . Allan B . Crawford . Ronald L . BMC Evolutionary Biology . 2 . 8 . 11972321 . Structural, functional, and evolutionary analysis of moeZ, a gene encoding an enzyme required for the synthesis of the Pseudomonas metabolite, pyridine-2,6-bis(thiocarboxylic acid) . 115864 . free .
4. 10.1023/A:1015241925322 . 2002 . Cortese . Marc S. . Paszczynski . Andrzej . Lewis . Thomas A. . Sebat . Jonathan L. . Borek . Vladimir . Crawford . Ronald L. . BioMetals . 15 . 2 . 103–120 . 12046919 . Metal chelating properties of pyridine-2,6-bis(thiocarboxylic acid) produced by Pseudomonas spp. And the biological activities of the formed complexes. 5545637 .
5. 10.1023/A:1024012015127 . 2003 . Budzikiewicz . H. . Biodegradation . 14 . 2 . 65–72 . 12877462 . Heteroaromatic monothiocarboxylic acids from Pseudomonas spp. 29898226 .
6. Ockels, W., Roemer, A., Budzikiewicz, H., Korth, H., Pulverer, G., "Bacterial constituents. II. An iron(II) complex of pyridine-2,6-di-(monothiocarboxylic acid) - a novel bacterial metabolic product", Tetrahedron Lett. 1978, 3341.