BIOSYNTHESIS OF THIAMINE

Abstract

2-Methyl-4-amino-5-hydroxymethylpyrimidine (OMPm) or 2-methyl-4-amino-5-aminomethylpyrimidine (AMPm) at 10-7 [image] together with 4-methyl-5-[beta]-hydroxyethylthiazole (MHT) was added to homogenates of sprouting peas, sprouting beans, clovers, potatoes, onions, scallions, and germinating radishes. The pH was adjusted to 5.0, and incubation followed for 3 hours at 37[degree]. The thiamine production was then determined. In the germinating radishes, 0.4[long dash]1.6 mg thiamine/10 g samples was produced after addition of OMPm and MHT, corresponding to a 26[long dash]77% increase of thiamine content. Sand culture of germinating radishes after addition of OMPm, AMPm, 2-methyl-4-amino-5-formylpyrimidine (FP) or 2-methyl-4-amino-5-carboxylic acid-pyrimidine (CAP) to MHT showed that OMPm was most effective for producing thiamine (more than twice as much being produced as the controls), followed by FP and AMPm. The same experiment using cysteine or methionine instead of MHT in the presence of OMPm resulted in less production of thiamine than with MHT. MHT, therefore, could not be replaced by cysteine or methionine. Thiamine production in germinating radishes in sand culture was further compared under 4 conditions: addition of OMPm alone; addition of both OMPm and MHT; addition of MHT alone; and without any addition. No marked difference was found among the 4 variations in weight, dry matter, length, and N content of the sprout, but, the amount of thiamine was about 3 times as great in the presence of OMPm and MHT, somewhat greater in the presence of OMPm, and about the same in the presence of MHT, as in the controls.