Jacques Mossé

The amino acid composition of wheat grain as a function of nitrogen content

Variation in the amino acid compositions of 30 samples of wheat (Triticum aestivum) grains from 12 different varieties was determined. Total nitrogen contents ranged from 1·4 to 3·3 % of grain dry matter. Amino acid contents were determined with maximum accuracy by employing three different times of hydrolysis in 6 m HCl for unoxidised samples so as to account for losses due either to degradation or incomplete release of amino acids. Accurate quantification of cyst(e)ine and methionine was achieved by performic acid oxidation prior to acid hydrolysis, and tryptophan was quantified after basic hydrolysis. Amide nitrogen content was determined following a fifth dilute acid hydrolysis. On a dry matter basis, amino acid content increased linearly as a function of nitrogen content with correlation coefficients often higher than 0·98. For a given amino acid, the same linear relationship was obeyed for the samples of a given genotype resulting from different environmental conditions as well as for samples from different genotypes. This enables prediction of the amino acid composition of any wheat from its nitrogen content. On a protein basis, amino acids varied as hyperbolic functions of nitrogen content. They increased for (glutamine+glutamic acid) proline and phenylalanine, they were roughly constant for leucine, isoleucine, serine, tyrosine, methionine and histidine and they decreased for the other amino acids. The degree of amidation (i.e. molar ratio of (Gln+Asn)/(Glx+Asx)), nitrogen to protein conversion factor, kA, and non-protein nitrogen to total nitrogen ratio (NPN/N) also varied as hyperbolic functions of nitrogen content. The degree of amidation and kA increased so slightly that they appeared to be practically constant (0·79 and 5·62, respectively) whereas NPN/N decreased from 61 × 10−3 to 33 × 10−3 within the range investigated.

Heterogeneity of avenin, the oat prolamin: Fractionation, molecular weight and amino acid composition

The prolamin, avenin, was extracted from oat seeds and shown to be maximally extractable in 45% (w/w) ethanol. A purification procedure is described and some properties of avenin are examined. As with wheat and barley prolamins, salt soluble and glutelin fractions were simultaneously extracted. Starch gel electrophoresis revealed two novel fractions, which were isolated by ion-exchange chromatography. These fractions have similar amino acid composition, threonine as the N-terminal amino acid and both have a 22 500 molecular weight. It is suggested that the avenin constituents have a common ancestral gene.

The amino acid composition of triticale grain as a function of nitrogen content: Comparison with wheat and rye

Triticale grains (19 samples from seven different varieties) with total nitrogen content, N, ranging from 1·7 to 3·7 % of grain dry matter, were analysed for their amino acid compositions with high accuracy from six different hydrolysates per sample. On a dry matter basis, amino acid contents in grain increased as linear functions of N with correlation coefficients higher than 0·97 for most of them in all the triticale genotypes and phenotypes studied. Hence, the amino acid composition of any triticale can be predicted from its N value. Protein amino acid contents changed as hyperbolic functions of N; contents of Phe, Pro, Glx and amide nitrogen increased, Leu, Ser and Tyr remained constant, and other amino acids decreased. The hyperbolic variations of the recovery of analyses, non-protein nitrogen content, degree of amidation and nitrogen to protein conversion factors were determined as a function of N. A comparison based on previous similar determinations on wheat and rye confirmed that triticale proteins are often intermediate between those of wheat and rye. However, they were richer than both parental species in essential amino acids for N less than 1·8 (Thr and Tyr), 2·0 (Tip), 2·5 (Met), 3·0 (Cys) and 2·3 (Lys).

RECENT RESEARCH ON MAJOR MAIZE PROTEINS: ZEINS AND GLUTELINS

Several authors have reviewed the different kinds of problems concerning seed proteins with more or less attention devoted to maize ones. We just mention some of them. From a biochemical point of view, a few papers treat of whole cereal proteins : Waldschmidt-Leitz and Metzner (1962), Wall (1964), Mossé (1968) and Inglett (1977). Other ones deal only with cereal prolamins (Mossé, 1966) or glutelins (Dimler, 1966) or even zein (Mossé, 1961). The most recent and completed one of Wall and Paulis (1978) concerns maize and sorghum proteins. From structure and localization point of view, Inglett (1970) reviews our knowledge on maize grain. Ory (1972) , Mascherpa (1975), Miège (1975b), Briarty (1978) and Pernollet (1978) discuss protein bodies. From a physiological point of view, Miège (1975c) considers seed development and Miège (1975d) , Ashton (1976) and Tomos and Laidman (1979) analyze germination and storage mobilization processes. From a genetic point of view. Nelson (1969) , Mertz (1972), Nelson and Burr (1973), Kaul (1973), Mossé (1978), Röbbelen (1979) and Thomson and Doll (1979) treat of plant breeding, particularly for better protein quantity and quality, while Mossé (1973) analyzes the nature and origin of plant protein heterogeneity and polymorphism. Such a polymorphism indeed enables the use of storage proteins as genetic markers in

Antigenic homologies between oat and wheat globulins

Total globulins of oat and wheat were compared by SDS‐electophoresis immunoblotting and in vitro protein synthesis experiments. Numerous homologies were found. The same 4 protein subgroups, with respect to molecular mass, were found in the two cereals. Immunoblotting with antibodies for total oat globulins allowed the detection of homologous proteins in each wheat protein group, especially in the 60‐kDa group, which corresponds to the major 12 S oat globulin. The same antibodies also reacted with in vitro synthesized proteins of the two cereals. However, compared to mature proteins, only a limited number of polypeptides react, suggesting that wheat globulins, like oat globulins, undergo post‐translational processes.

Polyacrylamide gel-urea electrophoresis of cereal prolamins at acidic pH

Abstract An electrophoretic procedure is described for vertical polyacrylamide gel-urea electrophoresis of cereal prolamins. The polyacrylamide gel is directly polymerized in potassium lactate buffer, pH 3.6, with an ammonium persulfate-silver nitrate system of catalysts, which enables one to control the polymerization of acrylamide. Electrophoresis is performed in aluminum lactate buffer, pH 3.6. Thus proteins are separated in a discontinuous system of buffers, which allows sample concentration at the beginning of the electrophoresis. Because the system acts in a very dissociating medium (6 m urea), any type of prolamins (e.g., gliadin, secalin, hordein, avenin, or zein) can be simultaneously analyzed and compared on the same gel slab. On the other hand, as is shown with barley prolamins, improved resolution is obtained, without any sample-reducing requirement during the same run, for both typical hordeins (B- and C-hordeins) and fast-moving low-molecular-weight proteins (A-polypeptides).

Variation of the amino acid scores and of the nitrogen-to-protein conversion factors in barley grain as a function of nitrogen content as compared with wheat and rye

Barley grains (9 samples from 7 cultivars) with nitrogen contents (N) ranging from 1.45 to 4.01% of dry matter were analysed for their amino acid (AA) composition with high accuracy from six different hydrolysates per sample. AA levels in grain increased as linear functions ofN with correlation coefficients close to unity. A comparison with literature data confirmed that the AA composition of any grain sample of normal barley can be predicted from itsN for all phenotypes and genotypes. AAs in grain protein changed as hyperbolic functions ofN which increased for Phe, Pro and Glx but more or less strongly decreased for the other AAs. By plotting AA scores againstN, barley proteins were shown to be always richer than wheat and rye in Val and Phe + Tyr; sometimes richer than both other species forN<2 (Lys); 2.2 (Leu and Ile); 3.4 (Thr); sometimes intermediate to wheat and rye above the latterN values. They were also intermediate in sulphur AAs forN<1.9 and drastically poorer forN>1.9. However, they were richer than both other species in Trp forN>1.6. The hyperbolic variations of non-protein nitrogen and nitrogen-to-protein conversion factors were determined as a function ofN and also compared with those of wheat and rye.

Relationships between nitrogen, amino acids and storage proteins in Lupinus albus seeds

Abstract Lupinus albus seeds (20 samples from 10 different lines or cultivars) with protein contents distributed from 23.8 to 48.4% were analysed for their amino acid composition with great accuracy (from 6 hydrolysates per sample). Amino acid levels in seeds increased as linear functions of nitrogen content with correlation coefficients close to unit in all the lupin genotypes and phenotypes. Hence the composition of any lupin seed sample can be predicted from its nitrogen content. Amino acid in total seed protein varied as hyperbolic functions of nitrogen content. The same was true for nitrogen-to-protein conversion factors. By controst, the composition of storage proteins accumulated in seeds remained constant and independent of seed protein content.

Constancy of composition of storage proteins deposited in Pisum sativum seeds

Abstract Proteins from Pisum sativum seeds with a wide range of protein contents were compared with regard to amino acid composition. The amino acids were determined with a high degree of accuracy in six different hydrolysates for each of the 33 samples studied. The results showed that the composition of the extra proteins deposited in the medium to high protein seeds remains perfectly constant regardless of the protein level, growth conditions or genotype of the peas.

Nature et fractionnement des protéines de l'Orge extraites par l'éthanol, l'isopropanol et le n-propanol à des titres différents

Summary Barley alcoholsoluble protein extractibilities by aqueous ethanol, isopropanol and n-propanol were measured at room temperature. The quantities extracted by each alcohol strongly depend on the concentration of the alcohol. The most efficient concentration for the three alcohols were by increasing order: 45 per cent ethanol, 40 per cent isopropanol, 35 per cent (w/w) n-propanol. Hordein preparations extracted by these three alcoholic solutions and by 75 per cent (w/w) ethanol were compared by means of the flour nitrogen percentage they contain and by electrophoresis, amino-acid analysis and Sephadex G 100 gel filtration. The preparations studied do not differ markedly in their amino-acid composition or electrophoretic pattern which shows at least 17 different bands. On the other hand, Sephadex G 100 gel filtration separates two main groups of proteins. The first one is present at the same level in all preparations studied and consists of electrophoretically typical hordeins (already described hordeins). The other group represents a fraction of the preparation, the more abundant as the solvent is more effective. This second group is excluded on Sephadex G 100 chromatography and does not give well defined bands by starch gel electrophoresis. Consequently it is related to some glutelins. Nevertheless its amino-acid composition is very close to the mean hordein composition. Electrophoretic comparison with glutelins extracted by acetic acid and with hordeins, all reduced and alkylated, discloses a great similitude between this fraction, the glutelins and some hordein fast components α, β and γ.