抄録
In the first report, it was shown that the protein of soy bean contained a far smaller amount of methionine than either protein of silk-worm pupa or that of sardine. As regards lysineand histidine-content, the second report showed that there was practically no difference among these proteins except that the lysine content of soy bean protein was a little lower than that of the others.
The present work has been carried out in order to compare these three proteins with one another as to their contents of the other indispensable amino acids, namely cystine and tryptophane. The determinations of cystine and tryptophane were carried out by using Okuda's iodine method for the former, amino acid and Tomiyama-Shigematsu method for the latter one. The results are shown in Table 1. In Table 1, (A), (B), and (C) show the proteins of silk-worm pupa, sardine, and soy bean, respectively. The cystine contents are given in the first column; the methionine contents are in the second and third columns where (1) denotes the isolated quantity and (2) denotes the calculated amount assuming that total sulfur is equal to a sum of cystine-sulfur and methionine-sulfur; the fourth column shows the tryptophane contents. It is shown that there are hardly any differences as to tryptophane contents among these proteins. It is worth while to notice that the protein of soy bean contains cystine much more than any of the other two proteins whereas a sum of cystine and methionine is almost the same in the three proteins.
