Methionine and Choline in a Simplified

OOYBEAN protein, as determined by ^ its amino acid distribution is known to be a fairly complete protein. Almquist, Mecchi, Kratzer, and Grau (1942) re-ported that the principal growth limiting factor in raw soybean protein is methio-nine and that heated soybean protein is slightly deficient in methionine for the chick at the 20 percent protein level. At this level no indications were obtained of a deficiency of other amino acids required by chicks but choline exerted a small growth promoting effect. Hayward and Hafner (1941) showed that autoclaving soybeans gave a nutritional response simi-lar to that obtained by adding cystine and methionine to raw soybeans. However, the greatest'response was obtained when either cystine or methionine or a combi-nation of the two were added to auto-claved soybeans. They concluded that raw soybean protein was deficient in avail-able cystine and that cooking made the cystine available. They also suggested that choline was involved in the process. Klose and Almquist (1941) obtained re-sults which indicated that chicks could synthesize methionine from the choline of soybean oil meal (or choline additions) only when homocystine was added to th