Threonine and the Odour of Protein Hydrolysates

Abstract

IT has been noticed repeatedly in this laboratory that many crystalline proteins such as chymotrypsin, serum albumin, etc., when hydrolysed in sealed tubes with 6 N hydrochloric acid at 120° C, gave a pleasant curry-like, spicy odour. A similar treatment of all the amino-acids found in proteins as well as β-alanine, α-amino-n-butyric acid, citrulline, ornithine and homocystine, showed that only threonine, allo-threonine and the derivative N-2.4.dinitrophenyl-threonine gave this odour. It was not detected in digests of threonine prepared at 110° C. in sodium hydroxide (0.005–5 N), 0.38N barium hydroxide, 18 per cent ammonium hydroxide, sulphuric acid (2–6 N), or nitric acid (0.25–2 N), but appeared weakly in 8 N acetic acid, 45 per cent formic acid and 45 per cent orthophosphoric acid digests.