Thiocyanate forming protein

Burow, M., Bergner, A., Gershenzon, J. and Wittstock, U. (2007) Glucosinolate hydrolysis in Lepidium sativum - identification of the thiocyanate-forming protein. Plant Mol. Biol., 63, 49-61. 

This compound is a bactericidal agent because it can oxidize the SH groups of structure-forming proteins and enzymes in bacteria. The LP system is used to prolong the shelf life of raw milk and pasteurized milk. H2O2 is produced here by the addition of glucose/glucose oxidase (cf. 2.7.2.1.1) and the concentration of thiocyanate is increased by addition. 

Oral exposure to cyanide usually results from accidental, homicidal, or suicidal ingestion of cyanide salts. Sodium cyanide and potassium cyanide are the most frequently studied cyanide compounds. Copper cyanide, potassium silver cyanide, silver cyanide, and calcium cyanide are other compounds that humans could encounter through oral or dermal exposure. Cassava roots and certain fruit pits contain compounds that can be broken down to form cyanide. Cassava roots form the staple diet of some populations in Africa, Central and South America, and Asia. However, it must be noted that cassava roots are notoriously deficient in protein and other nutrients and contain many other compounds, in addition to cyanide, that could be responsible for some of the observed toxic effects. Thiocyanate is a metabolite of cyanide that is formed in the body after exposure to cyanide compounds. When possible, all oral exposures are expressed as mg CN/kg/day. 

The total sulfur content of milk is about 360 mg/liter, of which about 300 mg/liter is in the cysteinyl and methionyl residues of milk proteins and about 35 mg/liter is inorganic sulfate, SO - (Table 1.1). The remainder, amounting to 25 mg of S per liter, is in the form of several organic compounds in which S is found in various states of oxidation. Thiocyanate ion (SCN-) frequently has been reported in milk. The concentra-... 

Thiocyanates are apparently only formed from three glucosinolates, benzyl-, allyl-, and 4-methylsulfinylbutyl-glucosinolate.13,14 The ability to produce thiocyanates seems to be restricted to just a few plant species, and, like epithionitrile formation, may require the presence of specific protein factors. 

Free thiocyanate anion formed (mole/mole protein). 

Grassmann and Hermann (1953) determined the COOH-terminal amino acids of collagen and gelatin using a modification of the thiohydantoin method of Schlack and Kumpf (1926). They first benzoylated the amino groups and then reacted the proteins with ammonium thiocyanate in acetic anhydride and acetic acid to form thiohydantoin derivatives. These could... 

CS reacts covalently with plasma proteins to form compounds that may be antigenic. On contact with water, it hydrolyses into o-chlorobenzaldehyde and malononitrile. The kidney excretes o-chlorobenzal-dehyde as the metabolites o-chlorohippuric acid (major) and o-chlorobenzoic acid (minor). The malononitrile is metabolized to thiocyanate. The cyano groups of 2-chlorobenzylidene malononitrile are unlikely to cause systemic cyanide toxicity since no significant amounts of free cyanide appear in the plasma. 

Cyanide is rapidly absorbed from the skin and all mucosal surfaces it is most dangerous when inhaled because toxic amounts are absorbed with great rapidity through the bronchial mucosa and alveoli. Once absorbed, distribution of cyanide through the body is rapid. Within a few minutes, cyanide is distributed through the body and its conversion to thiocyanate starts. The majority of cyanide in the body is protein-bound (60%). In sublethal doses, cyanide reacts with sulfane sulfur to form nontoxic... 

Typical organic precursors for COS, CS2 and the methylated sulfur gases include methionine and cysteine from proteins and isothiocyanates and thiocyanates from plant secondary metabolites. Methanethiol and DMS are also formed in anoxic freshwater sediments from reactions based on H2S and various methyl donors, for example, methoxylated aromatic acids, such as syringic acid from lignins. The rates of DMS emission per unit area are similar for both the oceans and Sphagnum-AommattA wetlands. Only the area of this peat land limited the relative importance of the latter source. 

Schlack-Kumpf method, also called the isothiocyanate method, a method for C-terminal sequence analysis of peptides and proteins. The C-terminus is converted with acetic anhydride into a 5(4H) oxa-zolone. Upon reaction with ammonium thiocyanate or with the new derivatizing reagent triphenylgermanyl isothiocyanate (TPG-ITC), Tacyl-2-thiohydantoins are formed, with the peptidyl residue being the acyl group. The peptidyl residue is then cleaved to give the 2-thiohydantoin derived from the C-terminal amino acid, which is subsequently analyzed [P. Schlack,... 

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