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. 2015 Mar 5:8:19-25.
doi: 10.4137/IJTR.S22444. eCollection 2015.

Conversion Percentage of Tryptophan to Nicotinamide is Higher in Rice Protein Diet than in Wheat Protein Diet in Rats

Katsumi Shibata  1 , Tsutomu Fukuwatari  1 , Tomoyo Kawamura  1
Affiliations

Conversion Percentage of Tryptophan to Nicotinamide is Higher in Rice Protein Diet than in Wheat Protein Diet in Rats

Katsumi Shibata et al. Int J Tryptophan Res. .

Abstract

We reported previously that the pellagragenic property of corn protein is not only low l-tryptophan concentration but also the lower conversion percentage of l-tryptophan to nicotinamide; the amino acid composition greatly affected the conversion percentage. The amino acid value of wheat protein is lower than that of rice protein. In the present study, we compare the conversion percentages of l-tryptophan to nicotinamide between wheat protein and rice protein diets in growing rats. The body weight gain for 28 days in rats fed with a 10% amino acid mixture diet with wheat protein was lower than that of rats fed with a 10% amino acid diet with rice protein (68.1 ± 1.6 g vs 108.4 ± 1.9 g; P < 0.05). The conversion percentage of l-tryptophan to nicotinamide was also lower for the wheat protein diet compared with the rice protein diet (1.44 ± 0.036% vs 2.84 ± 0.19%; P < 0.05). The addition of limiting amino acids (l-isoleucine, l-lysine, l-tryptophan, l-methionine, l-threonine) to the wheat protein diet improved growth and the conversion percentage. In conclusion, our result supports the thinking that the composition of amino acids affects the conversion ratio of l-tryptophan to nicotinamide.

Keywords: amino acid; nicotinamide; rice protein; tryptophan; wheat protein.

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Figures

Figure 1
Figure 1
Effects of amino acid mixture with wheat protein and with rice protein on body weight changes (A) and food intake (B) in rats. Note: Each symbol shows mean ± SE for 4–5 rats.
Figure 2
Figure 2
Association between urinary excretion of SUM and urinary excretion of Trp and its metabolites. Data from five groups were used for analyzing the association. (A) Urine SUM and urine Trp. (B) Urine SUM and urine 5-HIAA. (C) Urine SUM and urine Kyn. (D) Urine SUM and urine AnA. (E) Urine SUM and urine KA. (F) Urine SUM and urine XA. (G) Urine SUM and urine 3-HK. (H) Urine SUM and urine 3-HA. (I) Urine SUM and urine QA. (J) Urine SUM and urine Nam. (K) Urine SUM and urine MNA. (L) Urine SUM and urine 2-Py. (M) Urine SUM and urine 4-Py.
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