Polyphosphates

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Structure of the triphosphate ion

Polyphosphates are condensation products of salts of orthophosphoric acid (H 3 PO 4 ) with the general empirical formula M ' n + 2 P n O 3n + 1 and the structure

M′ – O– [P (OM ′) (O) –O] n –M ′

(M ′ = monovalent metal).

The polyphosphates also very often include the short-chain (i.e. actually oligo- ) phosphates. Cyclic polymers are called metaphosphates . The degree of polymerization can be several thousand.

Examples

with n = 3: adenosine triphosphate (ATP), pentasodium triphosphate Na 5 P 3 O 10

with n = 15 to 20: (NaPO 3 ) n ; often bears the factually incorrect name sodium hexametaphosphate .

n = hundreds to thousands: Volutin (stabilized with Ca 2+ , Mg 2+ ) in prokaryotes and in Acidocalcisomen in single-celled organisms - eukaryotes .

use

(NaPO 3 ) 15–20 was formerly the main component (besides metaphospates) of Calgon ™, a product for softening water in household appliances. The chemical often has the factually incorrect name of hexametaphosphate .

Polyphosphates in the food art as chelating agents , acid buffers , emulsifying salts , firming agents and stabilizers used.

Sodium, potassium, sodium calcium and calcium polyphosphate are approved in the EU as food additives with the number E 452 for certain foods, each with different maximum quantity restrictions. According to the Additive Admissions Ordinance , these are - largely uniform for most of the approved phosphates - individual specifications for a wide range of numerous different types of food. The maximum permitted amounts vary from 0.5 to usually around 5 to 50 grams per kilogram (in creamer for vending machines) or the lack of a fixed limit ( quantum satis - as required, for food supplements). Phosphorus is suspected of causing hyperactivity , allergic reactions and osteoporosis . A permissible daily dose of 70 milligrams per kilogram of body weight was set for the total amount of phosphoric acid and phosphates ingested.

Biological functions

All eukaryotic and prokaryotic cells contain polyphosphates. In bacteria and yeasts , the polymers are used to store energy and are stored in acidocalcisomes. Platelets contain homologous polyphosphate-storing structures called dense granules , which are rich in polyphosphates. The activation of platelets leads to the secretion of the polymers, which then start the formation of fibrin and the release of the inflammatory mediator bradykinin via activation of the blood coagulation factor XII ( Hageman factor , FXII) and thus have a procoagulant and proinflammatory effect.

properties

Polyphosphate molecules are labile. A hydrolysis is carried increases in temperature (to 60-70 ° C), a lowering of the pH (to pH 3.5-4), the presence of cations , or by raising the ionic strength in which they are conveyed to the medium.

literature

  • Müller et al., Platelet Polyphosphates Are Proinflammatory and Procoagulant Mediators In Vivo , Cell 139 (6): 1143-56; doi : 10.1016 / j.cell.2009.11.001 .
  • NJ Mutch: Polyphosphate as a haemostatic modulator. In: Biochemical Society transactions. Volume 44, number 1, February 2016, pp. 18-24, doi : 10.1042 / BST20150207 , PMID 26862183 .
  • PR Angelova, AY Baev, AV Berezhnov, AY Abramov: Role of inorganic polyphosphate in mammalian cells: from signal transduction and mitochondrial metabolism to cell death. In: Biochemical Society transactions. Volume 44, number 1, February 2016, pp. 40-45, doi : 10.1042 / BST20150223 , PMID 26862186 .
  • N. Lander, C. Cordeiro, G. Huang, R. Docampo: Polyphosphate and acidocalcisomes. In: Biochemical Society transactions. Volume 44, number 1, February 2016, pp. 1-6, doi : 10.1042 / BST20150193 , PMID 26862180 .

Individual evidence

  1. ^ Joseph W. Lengeler, G. Drews, Hans Günter Schlegel: Biology of the prokaryotes . Thieme, Stuttgart 1999, ISBN 3-13-108411-1 , p. 156 .
  2. ↑ Docampo R, Ulrich P, Moreno SN: Evolution of acidocalcisomes and their role in polyphosphate storage and osmoregulation in eukaryotic microbes . In: Philosophical Transactions of the Royal Society London, B, Biological Sciences . 365, No. 1541, March 2010, pp. 775-84. doi : 10.1098 / rstb.2009.0179 . PMID 20124344 .