Sulfur Amino Acid Content Research Articles

Lack of β-subunit of β-conglycinin in non-nodulating isolines of soybean

Abstract Soybean seed storage protein is a very important protein source for human and livestock, and its amino acid composition is well-balanced except for the low level of sulfur amino acids, methionine, and cysteine. β-Conglycinin (7S globulin) and glycinin (11S globulin) are the major storage proteins in soybean seeds, and β-conglycinin consists mainly of α′, α, and β-subunits and glycinin consists of acidic and basic subunits. It is generally recognized that the sulfur amino acid content is higher in the following sequence: acidic subunit >; basic subunit> α′-subunit >; α-subunit >; β-subunit (Wilson 1987).

PURIFICATION AND PARTIAL CHARACTERIZATION OF WHITE KIDNEY BEAN (PHASEOLUS VULGARIS) ?-AMYLASE INHIBITORS FROM TWO EXPERIMENTAL CULTIVARS

β-Amylase inhibitors WKB 858B and WKB 858B were purified to homogeneity from different cultivars of white kidney beans by extraction from the ground beans and by sequential heat treatment, ethanol fractionation, DEAE-cellulose chromatography, Sephadex G-75 gel chromatography and CM-cellulose chromatography. The inhibitors were homogeneous by 7.5% polyacrylamide gel electrophoresis; no isoinhibitors were found. Inhibitors WKB 858A and WKB 858B had isoelectric points of 5.0 and 4.65, respectively, and molecular weights of 42,000 and 20,000, respectively, by FPLC Superose 12 gel filtration chromatography. Inhibitor WKB 858A had molecular weights of 40,000 and 38,000 by Sephadex G-75 gel filtration chromatography and by native gel electrophoresis, respectively. Inhibitor WKB 858A contained 11.0% carbohydrate, N-linked to asparagine residues, with a composition of 1 fucose, 1 xylose, 4 galactose, 8 N-acetylglycosamine and 13 mannose residues per mol of inhibitor. Amino acid analysis of Inhibitor WKB 858A gave a high content of Asx, Glx, Ser, Thr and Val (combined total of 60% molar ratio) and low content of sulfur amino acids (0.8% molar ratio of Met and no 1/2 cystine). No-SH groups were found. The amino acid composition was similar to that of eight other a-amylase inhibitors from beans. Inhibitor WKB 858A formed a 1:1 stoichiometric complex with porcine pancreatic a-amylase with a Ki of 1.0 × 10−11 M at pH 5.4 and 30C; it had no trypsin inhibitory activity. At pH 6.90 and 30C, the rate of complex formation between Inhibitor WKB 858A and porcine pancreatic β-amylase was 2.76 times faster at 1.385 vs 0.035 ionic strength (with Na2SO4), indicating hydrophobic bonds are most important in complex formation.

Interaction of Dietary Protein Differing in Sulfur Amino Acid Content and Pectin on Bile Acid Conjugation in Immature and Mature Rats

Rapidly growing immature (4-wk-old) and slowly growing mature (15-wk-old) rats were fed fiber-free or 10 g/100 g pectin diets containing various proteins differing in the sulfur amino acid content for 30-32 d. Soybean protein, casein, whole egg protein and egg albumen were used at the nitrogen level of 2.7 g/100 g diet. These experimental diets contained 0.354, 0.540, 0.945 and 1.22 g sulfur amino acids/100 g, respectively. In the rats fed fiber-free diets, a substantial quantity of glycine-conjugated bile acids was detected in the bile of immature rats fed soybean protein and casein (73 and 25% of total bile acids, respectively), but not in the other groups (less than 13%). Dietary pectin increased bile acid excretion both in immature (48-77%) and mature (34-114%) rats irrespective of the protein source, except in immature rats fed egg albumen and mature rats fed whole egg protein. Because a pectin-dependent increase in bile acid excretion was essentially attributed to the increase in glycine-conjugates, this dietary fiber significantly increased the ratio of glycine-conjugates to taurine-conjugates (2.4- to 6.5-fold). This increase was accompanied by a 40-50% decrease in the concentration of liver taurine, except in immature rats fed soybean protein and egg albumen. However, there was no consistent relationship between the extent of taurine conjugation and the activity of liver cysteine dioxygenase, one of the rate-limiting enzymes in taurine synthesis.

Soy protein in relation to human protein and amino acid nutrition

The nutritional value of processed soy protein (isolated soy proteins and soy-protein concentrates) in human protein and amino acid nutrition is evaluated on the basis of a review of studies of growth and nitrogen balance in infants, children, adolescents, and adults. Findings show that well-processed soy-protein isolates and soy-protein concentrates can serve as the major, or even sole, source of protein intake and that their protein value is essentially equivalent to that of food proteins of animal origin. The importance of the sulfur amino acid content of soy protein for practical human nutrition is also examined from nitrogen-balance data. Under conditions of an anticipated normal usage of soy protein, methionine supplementation is not only unnecessary but may even be undesirable for young children and adults. However, for newborns, the data suggest that modest supplementation of soy-based formulas with methionine may be beneficial. Soy proteins have also been found to be of good quality to include in hypocaloric diets for weight reduction in obese subjects. Finally, the data indicate that soy proteins are well-tolerated and of good acceptability.

Factors affecting the requirement of dietary sulphur-containing amino acids of young pigs.

In the first of 3 experiments, requirement for total and digestible sulphur amino acids (SAA) was estimated in 240 pigs, 14 to 40 kg. A diet with low digestible amino acids content (digestible sulphur amino acids (SAA) 0.37%) was supplemented with all essential amino acids except methionine and 0, 0.05, 0.1, 0.1 or 0.2% synthetic DL-methionine added, providing diets with 0.42, 0.47, 0.52 and 0.57% digestible SAA. A control diet contained 0.52% digestible SAA. At similar levels of digestible SAA, there was no difference in performance between the experimental and the control diet, showing that optimum performance can be obtained with a less digestible diet supplemented with essential amino acids. Optimum performance was at 0.52% digestible SAA content in the diet, corresponding to about 0.65% total SAA. In experiment 2, 360 pigs 15 to 40 kg, were used to study SAA requirement at sub-optimal (0.60%) and optimal (0.70%) dietary threonine levels. Increasing threonine from 0.60 to 0.70%, increased (P

Biochemical and microbiological investigations of sigda—A Sudanese fermented food derived from sesame oilseed cake

Biochemical and microbiological changes during the fermentation of sesame (Sesamum inducum L) oilseed cake to produce the traditional Sudanese food sigda are reported. The microflora during fermentation was dominated by a homofermentative lactic acid bacterium Streptococcus sp, though initially the yeasts Candida sp and Saccharomyces sp were also present. The main fermentation product was lactic acid, the concentration of which attained 50 g kg−1 during fermentation. Acetic acid was also present at levels not exceeding 15 g kg−1. No other volatile fatty acids were formed in significant quantities. The accumulation of acids led to the pH of the mixture decreasing to 4.0 after 3 days. Dried sigda possessed a crude protein content of 440 g kg−1 and retained the high sulphur amino acid content of the sesame seed cake although lysine remained the most limiting amino acid nutritionally. The sigda fermentation was quite different from that of another Sudanese fermented food kawal, prepared from Cassia obtusifolia L leaves, and was also in marked contrast to the traditional oilseed fermentations practised in West Africa with respect to both the microflora and the products of fermentation. The traditional Sudanese fermented food furundu, prepared from the seed of karkade (Hibiscus sabdariffa L). was also examined. Initial findings suggest that the furundu fermentation isi ntermediate in character between that of sigda and kawal. It yielded a product iwth a crude protein content of 270 g kg−1, the protein being of excellent nutrition value with a chemical score of 80.

Influence of sulfur-amino acid content variation in plant vs animal protein on serum and tissue lipids in rats

The objective of the study was to determine the effects of methionine and cysteine supplementation of soy protein isolate and casein on serum and tissue lipid levels in rats. Sixty male, weanling, Wistar-Kyoto rats were fed two sources of protein (casein or soy protein isolate) and three variations of sulfur-amino acid supplementation (none, methionine, or cysteine). At this level of protein intake (10% by weight), rats fed soy-based diets had similar serum lipid concentrations than rats fed casein-based diets. Choline was not added to the diet in order to be able to assess independent influences of methionine and cysteine on lipid metabolism. Overall, serum lipid values were greater in rats fed proteins supplemented with methionine while the addition of cysteine produced lower lipid levels. Liver lipid concentrations were increased tremendously upon cysteine supplementation of soy protein isolate. Protein quality, as determined by protein efficiency ratio, was improved by supplementation of either sulfur-amino acid; however, methionine had the greatest effect. Results indicate that the sulfur-amino acids influence lipid metabolism in the absence of dietary choline. The mechanism by which this occurs is not known.

Influence of protein concentration on the sulphur‐containing amino acid requirement of broiler chickens1

Abstract 1. Two experiments were conducted with male broiler chickens from 3 to 6 weeks of age to determine the effect of dietary protein content on the requirement for sulphur amino acids (SAA). In experiment 1, 0, 0.5, 1.0 or 1.5 g DL‐methionine/kg were added to diets calculated to contain 200, 240 or 280 g protein/kg. In experiment 2, 0, 0.6, 1.2 or 1.8 g DL‐methionine/kg were added to diets calculated to contain 160, 180 or 200 g protein/kg. 2. In experiment 1, the SAA requirement for body weight gain increased as dietary protein content increased. Regression analysis indicated a requirement of 38 g SAA/kg protein. 3. In experiment 2 in which lysine supplementation provided a minimum of 10 g/kg, the requirement for SAA per unit of diet increased only slightly as protein concentration increased indicating that below 200 g protein/kg of diet, the SAA requirement increases per unit of protein with supplementation of the second‐limiting amino acid. 4. Abdominal fat percentage declined in a linear manner with each increment of SAA added to diets containing 160 to 200 g protein/kg. Adding methionine to diets containing 240 or 280 g protein/kg did not affect abdominal fat content. A lower limit of abdominal fat was achieved with a protein concentration of 240 g/kg. 5. It is concluded that the requirement for SAA of finishing broiler chickens is directly related to protein content at concentrations of 200 or more g protein/kg but increases per unit of protein at lower protein concentrations when a minimum lysine concentration is specified. Abdominal fat content reaches a minimum between 200 and 240 g protein/kg of a maize‐soyabean meal diet regardless of SAA content.

Estimation of sulfate and amino acid sulfur in plant material by X‐ray spectrometry

Abstract The SKα shift between the valences of sulfur has been used to determine by X‐ray spectrometry the two main forms of sulfur present in plant material, viz: oxidised S (S6+) and covalently bonded sulfur (Sc). S6+ and Sc were shown to correlate closely with sulfate, as determined by reduction with hydriodic acid, and cysteine+methionine S, respectively. The method is rapid and reliable provided the X‐ray spectrometer is stable and has high reproducibility in goniometer setting. The use of S6+ and Sc is recommended as an alternative to chemical methods for assessing the sulfur status of crops and the sulfur amino acid content of diets.

A comparison of the structure and properties of human, rat and rabbit serum transferrin

1. 1. The chemical and physical properties of human, rat and rabbit serum transferrins were compared. 2. 2. The proteins were found to differ in heat stability, iron release, their behaviour during electrophoresis in SDS polyacrylamide gels, and their sulphur amino acid content. 3. 3. The results are discussed in relation to the possible role of disulphide bridges in maintaining the shape and flexibility of the three transferrins, and in their appearance during the evolution of the transferrin family.

Enzymatic Release of Peptides, Methionine and Cystine from Dry Beans Following Various Heat Treatments

ABSTRACTGround Great Northern and pinto bean (Phaseolus vulgaris) samples were processed under varying conditions of time, temperature and pressure and then hydrolyzed in vitro using a mixture of trypsin, chymotrypsin and amino peptidase. The hydrolyzed samples were ultrafiltrated and the peptides (< 10,000 daltons) were collected and analyzed for their sulfur amino acid content (methionine, cysteine, and cystine). From 48% to 100% of the cysteine/cystine residues in the protein were released after 6 hr of enzymatic hydrolysis, whereas only 10% to 40.2% of the methionine residues were released during the same time period. The maximum rate of peptide release occurred at 3 hr of proteolysis, while the maximum rate of methionine and cysteine release occurred at 2 hr of proteolysis.

Feed intake and digestion responses in sheep to the addition of inorganic sulfur to a herbage diet of low sulfur content

Young sheep were used in feed intake and digestion studies with a wheaten straw diet of low sulfur (S) content (0.71 g S kg-1 organic matter) fed without additional S (low S diet) or containing sodium sulfate (high S diet). With the high S diet, relative to the low S diet, (i) the levels of sulfide in rumen liquor were elevated, (ii) less time was spent in ruminating activities, (iii) rumen liquor volume tended to be lower (-l0%), (iv) indigestible markers were cleared more rapidly from the rumen (approx. +16%), (v) more organic matter (OM) and acid detergent fibre were digested in the stomach and in the alimentary tract as a whole (+8-16%), (vi) more non-ammonia nitrogen (NAN) flowed into the intestines (+13%) and this NAN had a higher content of sulfur amino acids (+ 17%), (vii) a greater quantity of NAN was digested in the intestines per unit of digestible OM intake (+ 12%), (viii) the concentrations of various amino acids in venous blood were substantially lower, and (ix) fungal activity in the rumen was higher. The number of bites performed on each rumination bolus was inversely related to fungal activity in the rumen, but the latter was not related to OM digestibility or to the sulfur amino acid content of the NAN flowing into the intestines. The OM digestibility was inversely related to the rate of clearance of markers from the rumen with the low S diet but not the high S diet. Voluntary feed consumption was similar with both diets, and in the low S diet it was inversely related to OM digestibility and positively related to marker clearance rate from the rumen. Digestible OM intake under conditions of ad libitum feeding was higher with the high S diet (+11%) and positively related to fungal activity in the rumen and to the sulfur amino acid content of the NAN flowing into the intestines. The data indicate that an inadequate amount of S in the low S diet impaired the metabolism of the rumen microbiota which in turn affected variables relating to digestion and metabolism. A quantitatively significant role for the anaerobic fungi in the structural degradation of fibre is suggested and attention is drawn to the need for studies on both feed consumption regulation with low S diets and the relation between herbage S status and the sulfur amino acid content of the rumen microbiota.

Digestibility and Feeding Value of B858 Triticale for Swine

Nutritional value of B858 triticale cultivar as a replacement for corn and part of the soybean meal in swine diets was tested with 92 crossbred weanling (28 d) pigs. Pigs were assigned to one of four isolysine dietary treatments (TRT): 1) a fortified corn-soybean meal diet, 2) a fortififed B858 triticale-soybean meal diet, 3) a fortified B858 triticale-soybean meal with L-lysine HCl diet and 4) a fortified B858 triticale-soybean meal with L-lysine HCl and DL-methionine diet. B858 triticale contained (as-fed basis) 15.99% CP, .46% lysine, .18% methione and .36% threonine. During the started phase (weaning to 25 kg), there was a tendency for reduced ADG (P < .10) and increased feed/gain ratio (F/G; P < .05) for pigs fed TRT 3 compared with pigs fed TRT 1. The reduced performance may have been due to the marginal sulfur amino acid content of TRT 3. Over the grower-finisher phase (25 to 92 kg) and the entire study the F/G was greater (P < .05) for pigs fed TRT 2 than for pigs fed all other treatment diets. Chromic oxide was added to all diets of all pigs as an indigestible marker to estimate apparent digestion coefficients during the grower phase. Digestion coefficients were similar for DM and energy. Apparent digestion of ether extract was higher (P < .05) and of CP was lower (P < .05) for TRT 1 than for any other treatment. Digestibilities of phenylalanine, methionine, glutamic acid, tyrosine and glycine were lower (P < .05) from TRT 1 than from TRT 2, 3, and 4. The B858 triticale was palatable and had very low trypsin inhibitor activity. Because of its desirable amino acid composition and nutrient digestibility, it was an excellent grain for swine feeding.

The distribution and turnover of 35S methionine as influenced by diet in the dark-eyed junco ( Junco hyemalis)

1. 1. Dark-eyed Juncos ( Junco hyemalis) were maintained on one of three semi-synthetic diets, differing only in their sulphur amino acid content. 2. 2. 35S-methionine was administered intraperitoneally after 3 days on their respective diets and the animals were killed 24 or 96 hr post-injection. 3. 3. Faecal loss of 35S-methionine was significantly lower in the low methionine/high cysteine (HC) group after 24 hr when compared with the other two dietary groups (4.69 vs 5.53 and 5.47%), indicating a whole-body conservation of the limiting amino acid. 4. 4. Incorporation of 35S-methionine in hepatic and intestinal tissues was also greater in the HC group, even as the animals were losing body weight.

CDNA and protein sequence of a major pea seed albumin (PA 2 : Mr?26 000)

Pea albumin 2 (PA2:Mr≈26000) is a major component of the albumin fraction derived from aqueous salt extracts of pea seed. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and chromatography on DEAE-Sephacel resolve PA2 into two closely related components (PA2a and PA2b). A cDNA clone coding for one of these components has been sequenced and the deduced amino acid sequence compared with partial, chemically-determined sequences for cyanogen bromide peptides from both PA2 components. Complete amino acid sequences were obtained for the C-terminal peptides. The PA2 molecule of 230 amino acids contains four imperfect repeat sequences each of approximately 57 amino acids in length.The combined sequence data, together with a comparison of PA2-related polypeptides produced in vitro and in vivo, indicate that PA2 is synthesized without a signal sequence and does not undergo significant post-translational modification. Although both forms of PA2 contain Asn-X-Thr consensus sequences, neither form is glycosylated. Accumulation of PA2 contributes approximately 11% of the sulfur-amino acids in pea seeds (cysteine plus methionine equals 2.6 residues percent). Suppression of levels of PA2 polypeptides and their mRNAs in developing seeds of sulfur-deficient plants is less marked than that for legumin, in spite of the lower content of sulfur-amino acids in legumin.

Sulphur amino acid levels in some tissues of the rat during pregnancy and lactation.

Variations in free sulphur amino acid content in some rat tissues have been measured during pregnancy and lactation. As a general trend, sulphur amino acids tend to accumulate in tissues in late pregnancy. This accumulation is quantitatively more important in the liver and striated muscle than in the skin and the kidneys. Among sulphur amino acids, taurine shows the most marked changes, with a maximum accumulation in the liver and striated muscle on day 19 of pregnancy. After delivery, the levels of amino acids in the tissue pools show a tendency to drop, especially in liver and striated muscle. As expected, taurine shows the most marked decrease, returning to normal values in muscle but decreasing to depletion in the liver on day 20 after delivery. These results can be interpreted as follows: during pregnancy, increased food intake is sufficient to accommodate the metabolic needs of the mother, but during lactation, the requirements of milk synthesis promote the release of these amino acids from the tissues.

Membrane fluidity and phospholipid composition in relation to sulfur amino acid intake in brush border membranes of rat kidney.

The transport of ions and solutes across biological membranes may relate to changes in the lipid microenvironment of the membrane which could alter the activity or configuration of transport sites. Changes in the sulfur amino acid content of diets fed to young rats results in an increase in Na+-taurine symport in brush border membranes isolated from animals fed a low sulfur amino acid diet and a reduction in symport after a high taurine diet in comparison to uptake by membranes from normally fed animals ("the renal adaptive response"). We explored the possibility that diet-induced changes in brush border membrane symport relate to altered membrane fluidity and phospholipid composition in response to diet. An Arrhenius plot of initial rate (15 s) taurine uptake in breakpoint at 22 degrees C, but no change in relation to dietary alteration. Fluorescence polarization data employing the probe 1-6-diphenyl-1,3,5-hexatriene best fits a two-phase linear model employing a computer model fitting program. Dietary manipulations did not change the breakpoint upper segment slope or lower segment slope after incubating fresh membranes with DPH over the temperature range 4-56 degrees C. No change was evident in membrane phospholipid composition in relation to diet. This study indicates that the changes in initial rate Na+-taurine symport in relation to diet are less likely to be due to changes in the configuration of the transporter from an alteration of the lipid microenvironment of the membrane.

Nutritive value of malted millet flours

The changes in proximate composition, phytate phosphorus, thiamine and ascorbic acid content of finger millet, pearl millet and foxtail millet during progressive germination were studied. Germination resulted in a slight decrease in total protein and minerals, a marked fall in phytate-phosphorus and a significant increase in the ascorbic acid content of the millets. An increase in lysine and tryptophan but no appreciable changes in threonine and sulfur amino acid content of the millets were observed as a result of germination. However, the protein efficiency ratio values of ungerminated control seeds, 48 h germinated green malt and kilned malt were not significantly different.

The structure and complexity of the 11S polypeptides in soybeans

AbstractThe 11S soybean proteins called glycinin are isolated as a 350,000 dalton complex that consists of six nonidentical subunits. Each subunit consists of an acidic polypeptide component linked to a basic component by a single disulfide bond. Initial translation products of glycinin subunits are single polypeptides of ca. 60,000 daltons that undergo both co‐ and posttranslational modification. The precursors have a short signal sequence, followed by the acidic component, a short linker polypeptide, the basic component and a short trailer peptide. Five major subunit types have been purified and characterized by amino acid sequence analysis. While all of them are clearly synthesized by a family of homologous genes, they can be separated into two groups based on sequence homologies. Group I subunits (A1aB2, A1bB1b, A12B1a) are uniform in size (Mr = 58,000), relatively rich in methionine, and exhibit ca. 90% sequence homology among members in the group. The group II subunits (A3 B4, A5A4B3) exhibit a similar level of homology among themselves, although they contain less methionine and are larger (Mr ″ 62,000–69,000) than group I subunits. Sequence homology between a member of one group and a member of the other is only 60–70%. Since the sulfur amino acid content of subunits is variable and genetic polymorphism in subunit composition has been documented, alteration of the functional and nutritional properties of these seed proteins by genetic manipulation may be possible.

Choline requirement of the preruminant lamb during the first two or three weeks of life

Preruminant male crossbred lambs, aged 1-2 days at the start of the experiment, were bottle-fed on milk replacers containing casein as the sole source of protein for an experimental period of 15-21 days. Choline-deficient diets were used in experiment 1 to determine the effect on the performance of the lambs of thc dictary protein concentration (10, 15 and 25% protein energy), and in experiment 2 of different sources of fat (butter oil, maize oil or lard), unsupplemented, or with supplements of choline chloride or L-cystine. Supplements of choline chloride decreased liver fat content and decreased urinary creatine excretion, irrespective of dietary protein concentration or source of dietary fat. Ira general, urinary ammonia excretion increased as the sulfur amino acid content of the diets increased, but there were interactions with the source of fat, so that although sulfur intake remained constant ammonia excretion was higher with diets containing lard than with those containing maize oil or butter oil. The effect of the supplements of 1,-cystine on liver fat content and urinary creatine excretion was not significantly different from that of the unsupplemented choline-deficient diets. In experiments 3 and 4 a choline-deficient diet with 25% protein energy and butter oil as the source of fat was supplemented with graded amounts of choline chloride. Energy intake was ad libitum, or restricted to 80% of ad libitum. When the lambs were fed ad libitum there was a significant decrease in liver fat content even with the smallest supplement of choline chloride (c. 9 mg MJ-1 gross energy), but no significant effect when energy intake was restricted. Since liveweight gains and nitrogen balances were unaffected by the presence or absence of the choline supplements it was concluded that in milk replacers containing 25% protein energy from casein, with butter oil as the source of fat, supplementation with choline chloride to provide 9 mg MJ-1 gross energy (233 mg kg-1 dry matter) would be sufficient to prevent the increased deposition of fat in the liver during the 6rst three weeks of life.