SULPHUR METABOLISM

METABOLISM OF SULPHUR

1. Sulfur Metabolism Gandham . Rajeev

2. Sulfur is an essential element & is a component of several biologically important compounds. Proteins contain about 1% sulfur by weight . The sulfur is made available to the body by the proteins containing methionine , cystine or cysteine . These three amino acids are sulfur containing amino acids

3. Sulfur is also available from S-containing B-complex vitamins viz. thiamine (TPP), coenzyme A, lipoic acid and biotin . Certain sulpholipids and glycoproteins ( mucoitin and chondroitin sulfate, heparin) also provide sulfur

4. Dietary sources Sulfur is present in the food as inorganic sulfate and organic sulfate (proteins, amino acids and peptides). Major sources are proteins rich in methionine and cysteine . Absorption: Sulfur is ingested as organic sulfates as in proteins or as inorganic sulfates. Inorganic sulfate is absorbed as such from the intestines, while sulfur containing amino acids are absorbed by active transport

5. Biochemical functions Formation of active sulfate (PAPS): 3- Phosphoadenosine 5-phosphorsulfate(PAPS) is the active sulphate, utilized for several reactions e.g. synthesis of glycosaminoglycans (GAGS), detoxification mechanism . Sulphur-containing amino acids are very essential for the structural conformation and biological functions of proteins (enzymes, hormones, structural proteins etc.).

6. The disulphide linkages (-S-S-) and sulfhydryl groups (-SH) are largely responsible for this The sulfur-containing amino acid methionine (as S- adenosylmethionine ) is actively involved in transmethylation reactions and S- adenosylmethionine also acts as the initiator in initiation process of protein synthesis .

7. Iron-sulfur proteins are found in electron transport chain. Sulfur containing vitamins such as biotin, pantothenic acid, thiamine, lipoic acid are involved as coenzymes .

8. Excretion Sulfur is excreted by the kidneys in urine in the form of inorganic, organic and ethereal sulfate. Sulfur is oxidized in the liver to sulfate and excreted. The unoxidized sulfur is in the form of sulfur containing amino acids, thiocyanates etc.

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