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The poor nutritional performance of rats fed raw soya-bean-containing diets appeared to be due to reduced apparent digestion and absorption of dietary protein, coupled to changes in systemic metabolism leading to a poor overall nitrogen balance. Aqueous heat treatment greatly reduced but did not eliminate the antinutritional effect. Heat treatment with aqueous ethanol was more effective. The whey protein (pH 4.8 soluble extract) fraction contained the bulk of the trypsin inhibitor and haemagglutination activity and gave the poorest net protein utilisation value. However, an eight-fold increase in trypsin inhibitor content did not significantly effect apparent nitrogen digestibility. Therefore inhibition of gut proteolytic enzyme activity in vivo by soya bean trypsin inhibitors did not account fully for the poor nutritional performance. The problems elicited by soya bean are not transitory and thus there was a cumulative deterioration in overall performance for 16 weeks as a result of continuous exposure to soya bean.

The complete amino acid sequence of the major a subunit of the lectin from seeds of Dioclea grandzflora was determined. The sequence was deduced from analysis of peptides derived from the native a subunit by digestion with trypsin, chymotrypsin, the Staphylococcus aureus V8 protease, and pepsin; and from larger peptides produced by digestion of the citraconylated protein with trypsin. The a subunit consists of a single polypeptide chain of 237 amino acids which differs from the sequence of concanavalin in 53 positions. Significant levels of heterogeneity were observed in five positions in the sequence.Seeds of Dioclea grandiflora (mucang), an interesting and potentially valuable legume seed from the North East of Brazil, contain a number of closely related lectins which have been characterized recently [I] and shown to belong to the general group of D-mannose@-glucose)-binding lectins [2]. It was also shown that the D. grandzjlora lectins were similar to the wellcharacterized concanavalin A from Canavalia ensiformis in that they had a requirement for the presence of Ca2+ and Mn2+, lacked covalently bound carbohydrate, and had a similar amino acid composition, molecular mass and subunit structure, but differed distinctly in having high PI values in the region of pH 8.6 -9.0. Like concanavalin A the lectins from D. grandiflora could be dissociated in the presence of SDS to yield three subunits a, j, and y of approximate relative molecular mass 25 -26 000, 13 -14000 and 8 -9000 when examined by SDS-PAGE. The full molecule at neutral pH values appeared to have the composition of a,j,y, but at low pH values it seemed likely that this was split symmetrically into two half-molecules of apy.Whilst the amino acid sequences of several lectins belonging to the tribe Vicieae have been determined [3 -101 until now the only primary structure known for a lectin from the tribe Diocleae is that for concanavalin A [l 1 -121. We now wish to report the complete sequence of another lectin from this tribe, the major a subunit of the lectin from D. grandiflora which although it shows close similarity with the concanavalin A sequence nevertheless differs in 53 amino acid positions. MATERIALS AND METHODSDioclea grandiflora (Mart) seeds were collected in the state of Ceara, Brazil. The initial purification of the lectin was as Abbreviations. SDS, sodium dodecylsulphate ; PAGE, polyacrylamide gel electrophoresis; HPLC, high pressure liquid chromatography; dansyl, 5-dimethylamino-naphthalene-l-sulphonyl ; DABITC, 4-N, N-dime thylaminoazobenzene-4'-iso thiocyanate.Enzymes. grandzflora lectin were dissolved in 1 ml of 3 % SDS, heated at 100 "C for 10 min and applied to the column, which was eluted at a flow rate of 8 ml/h. The size of the fractions collected was 1.2 ml. The intact a subunit emerged from the column at 1.71 x void volume, whilst the j and y subunits were eluted together at 1.99 x void volume. After one re-chromatographic step the a subunit contained only one component when examined by SDS-PAGE (with an apparent M , of 25 -26 ...

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