The origin of the sulfur atom of thiamin.
The incorporation of the sulfur atom of 35S-labeled amino acids into thiamin in Escherichia coli and Saccharomyces cerevisiae was studied. The specific radioactivity of the S atoms was incorporated at similar levels into thiamin and cysteine residues in cell proteins. However, the specific radioactivity of the S atoms from [35S]methionine was not incorporated into thiamin but into methionine residues in cell proteins. Thus, the origin of the S atom of thiamin was established as being the S atom of cysteine. No activity from [U-14C]cysteine was recovered in thiamin, proving that the carbon skeleton of this amino acid was not utilized in synthesizing the thiazole moiety of thiamin.
D002250:Carbon Radioisotopes; D003545:Cysteine / Q000378:metabolism; D003553:Cystine / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013462:Sulfur Radioisotopes; D013831:Thiamine / Q000096:biosynthesis* / Q000302:isolation & purification
D002250:Carbon Radioisotopes; D013462:Sulfur Radioisotopes; D012694:Serine; D003553:Cystine; D008715:Methionine; D003545:Cysteine; D013831:Thiamine