The Amino‐acid Composition of Certain Seed Proteins

Abstract

A survey of the literature based on the accumulated data of Block and Boiling (1951) indicates that knowledge of the amino-acid composition of the proteins of legume seeds is limited. There is an almost complete lack of comprehensive data for the seeds of legumes of particular importance to Australian agriculture, such as lupins, vetches, peas and subterranean clover. Investigations of the digestibility and biological value of the protein of some of these seeds, using nitrogen balance methods, have been reported from this laboratory for the growth of sheep (Williams and Moir, 1951) and for the growth of the rat (Smythe, 1950) but they were not supported by any extensive data on their amino-acid composition. The arginine content of these seed proteins was, however, reported by the author (Holmes, 1951) and the cyst(e)ine and methionine contents of some of them by Johanson (1948).In recent years considerable attention has been devoted to the sulphurcontaining amino-acids in seed proteins (Lugg, 1945 and 194C; Johanson and Lugg, 1946). As a result it has beeii establislied that legume seeds and their bulk proteins are of very low or low methionine content and their cyst(e)ine values range from very low to moderately high. Numerous feeding trials indicate that the methionine contents of legume seeds may constitute a first limiting factor in nutrition, at least in the rat and the chick.' On the other hand, in spite of the not unexpected emphasis placed on the sulphur-containing amino-acids in wool growth (Marston, 1935) no correlation could be found by Johanson (loc. cit.) between cyst(e)ine + methionine fed and wool growth in the series of feeding trials carried out by Stewart and Moir (1947). In these trials marked differences were found between different protein sources, including several legume seeds, in promoting wool growth in Merino sheep when these proteins were fed at the same overall level of nitrogen intake and constituted almost the whole of the nitrogen of otherwise similar rations. The possibility of other essential amino-acids limiting the wool-growing capacity of these proteins, particularly those occurring in wool keratin in high proportions,, namely arginine, leucine and threonine, could not be excluded. The present study of the amino-acid composition of certain legume seed proteins and of linseed protein.

Ruminal Flora Studies in the Sheep V. the Amino Acid Composition of Rumen Bacterial Protein

“…Support for this contention is given by the fact that Block and Mitchell (1946) report the figure of 96 for the B.V. of whole egg protein in the rat, compared with 86.7 obtained by Williams and Moir (1951) for this protein in growing lambs. Further, with linseed protein, in which the amino acid composition is, on our data and those of Holmes (1953), rather similar to that of rumen bacterial protein, the B.V. for growth in both the rat and the sheep are closely similar. Thus Block and Mitchell give the value of 78 for rats and Williams and Moir the value of 79.7 for lambs.…”

“…Thus Block and Mitchell give the value of 78 for rats and Williams and Moir the value of 79.7 for lambs. Williams and Moir have also found no significant difference between the B.V. of linseed meal protein and subterranean clover seed protein in lambs, in spite of the much better essential amino acid make-up of the former (Holmes 1953). Moreover these workers obtained for urea a B.V. of 69 where this source of N constituted approximately half the dietary N of lambs, and Loosli et al (1949) a B.V. of 46 where urea constituted the sole dietary source of N to lambs.…”

“…A comparison with more common sources of protein taken from the data of Holmes (1953), using the "total per cent. deficit" of essential amino acids in each case as described by Mitchell and Block (1946), indicates that rumen bacterial protein is inferior to vetch and lupin seed protein, of similar value to linseed and meatmeal, slightly superior to pea seed, and markedly superior to subterranean clover seed protein.…”

“…Substantial hydrolytic losses have been obtained with these amino acids in an experiment conducted in this laboratory. The actual losses and the conditions of the experiment are being published elsewhere (Holmes 1953) since they do. not relate directly to the rumen bacterial protein preparations under investigation.…”

Physiology of Pea Fruits

“…Hyde (1953), using chromatographic methods, confirmed the predominance of asparagine in the hulls and of arginine in the seeds of developing peas and listed a number of other compounds. It may be noted that arginine is the chief amino acid liberated on the hydrolysis of protein from pea seeds (Holmes 1953). Snellmann and Danielsson (1953) recorded the presence in developing pea seeds of peptides containing two to six amino acid residues.…”