2,6-Pyridinedicarbothioic acid (PDTC) is an
organosulfur compound that is produced by some bacteria. It functions as a
siderophore, a small
chelating agent with a high affinity for
iron. Siderophores are deployed as
ion scavengers for
microbes. Siderophores solubilize compounds by forming strong complexes. PDTC is secreted by the
soil bacteria ''
Pseudomonas stutzeri'' and ''
Pseudomonas putida''.
Synthesis and biosynthesis
PDTC can be synthesized by treating the pyridine-2,6-dicarboxylic acid (or its diacid dichloride) with H
2S in dry
pyridine:
:NC
5H
3(COOH)
2 + 2 H
2S → NC
5H
3(COSH)
2 + 2 H
2O
This produces an orange 1:1
pyridinium salt of 2,6-pyridinedicarbothioate. Treatment of this salt with acid give PDTC, which can then be extracted with
dichloromethane
Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with ...
.
The biosynthesis of PDTC remains unclear although some insights can be deduced from the genetics. It is suggested that ''Pseudomonas stutzeri'' may have acquired at least one of the genes by lateral transfer from
mycobacteria
''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') and ...
.
In a proposed biosynthetic sequence pyridine-2,6-dicarboxylic acid, a known bacterial metabolite,
[ is activated as its bis-adenosine monophosphate (AMP) derivative. The sulfur donor and its activation remain uncertain.]
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.[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. ] It is iron selective[ 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.][
]
See also
* Dipicolinic acid
References
{{DEFAULTSORT:Pyridinedicarbothioic acid, 2,6-
Organosulfur compounds
Pyridines