Conversion ratio of tryptophan to niacin in rats fed a vitamin B1-free diet.
The effect of a vitamin B1-free diet on the conversion ratio of tryptophan to niacin in rats was investigated using the current methods for determination of the intermediate metabolites. Rats were fed with diets with or without B1 for 33 days. The body weight gain and food intake in the B1-free group were almost the same as the control group for 10 days, but, they steeply dropped after that time and the conversion ratio of tryptophan to niacin began to increase. The ratio reached 7-fold that of the control group on the last day of the experiment. This finding seriously differed from the previous reports, which described that B1 was needed in the first part of tryptophan conversion to niacin and that the conversion ratio of tryptophan to niacin decreased in B1-deficient rats. Furthermore, the activity of tryptophan oxygenase, in which it was reported that B1 is required for the tryptophan catalytic reaction, did not decrease but increased even when the B1-free diet was fed. These results suggest that there is a very small possibility of the direct involvement of B1 in the conversion of tryptophan to niacin.
Shibata
K
K
Department of Human Health Science, Faculty of Human Sciences, Osaka International University for Women, Japan.
Kondo
T
T
Yonezima
M
M
D000818:Animals; D004032:Diet; D008297:Male; D009525:Niacin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013831:Thiamine / Q000008:administration & dosage* / Q000502:physiology; D014364:Tryptophan / Q000378:metabolism*; D014366:Tryptophan Oxygenase / Q000378:metabolism
D009525:Niacin; D014364:Tryptophan; D014366:Tryptophan Oxygenase; D013831:Thiamine