Biomedical subjects

H D Belitz

Publications and source records attributed to H D Belitz.

At least 19 recordsLinked to original sources

PubMed1993

Primary structures of proteinase inhibitors from Phaseolus vulgaris var. nanus (cv. Borlotto).

The primary structures of two trypsin-chymotrypsin inhibitors from Phaseolus vulgaris var. nanus (bush bean, cv. Borlotto), PVI-3(2) und PVI-4, were derived from automated Edman degradation data, amino acid composition and manual Edman degradation results of enzymatic fragments and homology with other Bowman-Birk type proteinase inhibitors. The highest degrees of homology were observed between PVI-3(2) or PVI-4 and the trypsin-chymotrypsin inhibitors from lima beans (LBI I, IV and IV', 86%), black-eyed peas (BTCI, 81%), and, in part, adzuki beans (ABI I, II and II', 74-77%). Similarly, the primary structure of the trypsin-elastase inhibitor from the same source, PVI-3(1), was deduced which showed highest homology with that of the trypsin-elastase inhibitor GBI II from garden beans (92%), followed by GBI II' from garden beans (86%) and C-II from soybeans (71%). In contrast, homology between PVI-3(2) and PVI-4 on the one hand and PVI-3(1) on the other was relatively low (61%).

Amino Acid Sequence↗

PubMed1993

Bitter taste of enzymic hydrolysates of casein. I. Isolation, structural and sensorial analysis of peptides from tryptic hydrolysates of beta-casein.

beta-Casein A2 was isolated from milk of a homozygous cow and hydrolysed with trypsin. The hydrolysate was separated by RP-HPLC into 18 peptides, all but one of which could be attributed to the sequence of beta-casein on the basis of the amino acid composition. Some peptides overlapped. In total, they represented about 97% of the protein sequence. Only three peptides had a bitter taste, namely I49-N68 (recognition threshold 1.0 mg/ml, 0.45 mmol/l), I49-K97 (1.5 mg/ml, 0.28 mmol/l) and G203-V209 (0.175 mg/ml, 0.23 mmol/l). The contribution of the three peptides to the overall bitterness of the beta-casein hydrolysate (2.67 mg/ml) was about 11, 21, and 60%, respectively. Peptide I49-K97 was present in the hydrolysate together with its fragments I49-N68 and S69-K97. Remarkably, the smaller and more hydrophobic fragment I49-N68 was less bitter than I49-K97 on a molar basis, whereas the larger and more hydrophilic fragment S69-K97 had a neutral taste. These results show that in the case of larger peptides neither hydrophobicity nor size are responsible alone for bitter potency, but that conformational parameters must be of great importance. Furthermore, it can be concluded that only a part of the structure is responsible for the contact with the receptor. The bitterness of G203-V209 is discussed in connection with related synthetic peptides in the literature.

Amino Acid Sequence↗

PubMed1993

Disulphide bonds in wheat gluten: further cystine peptides from high molecular weight (HMW) and low molecular weight (LMW) subunits of glutenin and from gamma-gliadins.

Glutenin was prepared from gluten of the wheat variety Rektor by extraction of gliadin with aqueous ethanol. It was cleaved successively into soluble peptides by the enzymes trypsin and thermolysin. Separation of the peptide mixtures was performed by gel permeation chromatography (GPC) on Sephadex G25 and reversed phase high performance liquid chromatography (RP-HPLC) on ODS-Hypersil. Cystine peptides were detected by differential chromatography of the samples prior to and after reduction. After isolation by multi-step RP-HPLC, the cystine peptides were reduced. The resulting cysteine peptides were alkylated with 4-vinylpyridine, separated by RP-HPLC and sequenced by means of the Edman degradation. The isolated cystine peptides represented a considerable portion of the total cysteine in glutenin: four out of seven cysteine residues of HMW subunits, and eight out of nine cysteine residues of LMW subunits are documented by at least one cystine peptide. Most of the peptides corresponded to known sequences of gluten protein components. From the structures of some tryptic peptides, inter- and intramolecular disulphide bonds for HMW subunits of glutenin have been proven. Cystine peptides from the thermolytic digest have been assigned to LMW subunits of glutenin and to gamma-gliadins. Other peptides have been closely related to partial sequences of these protein components. The results have allowed several conclusions about the arrangement of intra- and intermolecular disulphide bridges in gluten proteins.

Amino Acid Sequence↗

PubMed1993

Monitoring cheddar cheese ripening by chemical indices of proteolysis. 3. Identification of several high-molecular mass peptides.

Two Cheddar cheeses from two different production plants were ripened over 24 weeks at 10 degrees C and then analysed for peptides soluble in citrate buffer at pH 4.6 by reversed-phase (RP)-HPLC. Thirteen peptides with a chain length of between 35 and 65 amino acid residues and molecular masses between 3800 and 7400 were isolated and assigned to the corresponding amino acid sequences of the casein fractions via Edman degradation and amino acid composition. All peptides were fragments of the region K29-S96 of beta-casein A1 and A2, and eleven of them had M93 as the C-terminal. The amounts and proportions of these peptides varied differently during ripening of the two cheeses, so they may be suitable markers for characterizing the stage of ripening.

Amino Acid Sequence↗

PubMed1992

Characterization of the gliadin-derived peptides which are biologically active in coeliac disease.

Reversed-phase HPLC on C18 silica gel at pH 3.5 was used to separate peptides in fraction 9, a mixture of peptides of unknown composition obtained from an enzymic digest of wheat gliadin. This fraction, which has been shown to be toxic to individuals with coeliac disease, yielded a principal peak as well as many minor peaks after HPLC. The significant peaks were subjected to amino acid analysis. The principal peak obtained was purified by rechromatography at pH 6.0 and shown to contain a dodecapeptide of sequence H-Arg-Pro-Gln-Gln-Pro-Tyr-Pro-Gln-Pro-Gln-Pro-Gln-OH. This peptide may have been derived from regions in the A-gliadin molecule corresponding to amino acids numbered 75-86 or from homologous regions in other gliadin molecules. Preliminary results indicate that it is active in two in vitro models of coeliac disease and that it could be the source of one of the undigested peptides (Hexapeptide II, (Glx)3, (Pro)2, Tyr) obtained from coeliac mucosal digestion of fraction 9. Some active serine-containing peptides were also obtained from chromatography at pH 3.5 and attempts are being made to correlate these with the other undigested peptide (Hexapeptide I) of composition (Glx)3, (Pro)2, Ser, obtained after coeliac mucosal digestion of fraction 9.

Amino Acid Sequence↗

PubMed1992

[Comparative studies of the Osborne protein fraction of wheat varieties with different dough and baking properties].

The proteins of flours from the wheat varieties Clement (CLE) and Disponent (DIS), which are characterized by substitution of the wheat chromosome 1B by the rye chromosome 1R (CLE) and by 1BL/1RS-translocation of chromosome segments (DIS), respectively, and which yield sticky doughs, were extracted by the Osborne procedure and compared with the good variety Kolibri (KOL). CLE and DIS delivered significantly higher amounts of water-soluble proteins (31.2 and 23.2% of the total protein) than KOL (15.5%). The proportions of ethanol-soluble proteins were approximately constant for the three varieties (31.5-33.9%) while the amounts of residual proteins after extraction with ethanol were significantly different (CLE, 16.8%; DIS, 21.6%; KOL, 26.4%). Water extracts as well as residues exhibited also marked differences in their amino acid compositions. Investigation of the water extract from DIS by gel permeation chromatography and by RP-HPLC showed the presence of prolamins: omega 1,2-gliadins and/or omega-secalins could be detected on the basis of amino acid composition and N-terminal amino acid sequence. In the case of good varieties such as KOL, these prolamins seem to remain partially in the residue of the ethanol extract under the conditions of the classical Osborne procedure, whereas they are found in the water extract in the case of such varieties as CLE and DIS. On the other hand, a modified Osborne procedure (salt/ethanol/acetic acid) delivered the prolamins, which correspond to 39-40% of the total protein, completely within the ethanol fraction in the case of all three varieties.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Isolation and enzymatic fragmentation of the coeliac-active gliadin peptide CT-1.

Investigations on the structure/toxicity relationships of gliadin peptides were continued with the coeliac-active gliadin peptide CT-1, which is derived from the N-terminal portion (residues 3-24 of the amino acid sequence) of alpha-gliadins [this journal (1986) 182:115-117]. CT-1 was produced by chymotryptic digestion and reversed-phase (RP) HPLC from the peptide fraction G3 [this journal (1992) 194:1-6] and digested with the proteases endoproteinase Glu-C, pancreatin, papain and thermolysin. The fragment peptides were separated by preparative RP-HPLC and characterized by amino acid analysis. On the basis of the specificity of the enzymes for CT-1 and the toxic effect of enzymatic hydrolysates of gliadin described in the literature, the significance of partial sequences, in particular of the sequence -Pro-Ser-Gln-Gln-Gln-Pro- for the coeliac-toxicity effect, is discussed.

Amino Acid Sequence↗

PubMed1992

Coeliac active peptides from gliadin: large-scale preparation and characterization.

Larger amounts of coeliac active peptides are required for pathogenetic investigations. Therefore, a simplified preparative procedure by means of gel-permeation chromatography and reversed-phase HPLC was developed for the isolation of the peptides B3141-B3146, which are present in peptic tryptic digests of gliadin [this journal (1983) 176:85-94]. The peptides are derived from the N-terminal part of alpha-gliadins and are closely related. The amino acid sequence of B3143 is VPVPQLQPQNPSQQQPQEQVPLVQQQQFPGQQQQFPPQQPYPQPQPFPSQQPYL. B3144 has proline instead of glutamine in position 34. The previously described peptide B3142 [this journal (1984) 179:371-376] corresponds to B3144 except for the missing C-terminal leucine.

Amino Acid Sequence↗

PubMed1991

[Analysis of food and feed by partial sequences of characteristic protein components (carrier peptides). 1. Isolation and structural determination of wheat-specific peptides from chymotryptic hydrolysates of gliadin].

Gliadins from wheat flour were extracted with 70% aqueous ethanol and hydrolyzed with alpha-chymotrypsin. Eight peptides, which seemed adequate as specific indicators for wheat ('Leitpeptide'), were isolated from the partial hydrolysate by RP-HPLC and analyzed for their amino acid sequences. Six of them were attributed to gliadin sequences already described in the literature, whereas two peptides represented novel sequence variations. Parallel investigations on the corresponding partial hydrolysates of prolamins from rye, barley, oats and maize showed that the isolated peptides were specific for wheat. A search in the protein data bank MIPS X (as of January 23 rd, 1990) did not produce any identical sequence. The 'Leitpeptide' allows the sensitive and specific recognition of wheat in complex and heated systems by RP-HPLC. They could be used also as the basis for immunochemical tests which would be convenient in routine analysis.

Amino Acid Sequence↗

PubMed1991

Disulphide bonds in wheat gluten: isolation of a cystine peptide from glutenin.

Gluten from the wheat variety Rektor was extracted with 70% aqueous ethanol. The residual protein (glutenin) was hydrolysed with trypsin. The partial hydrolysate was separated into seven fractions by gel permeation chromatography on Sephadex G 25. Four cystine-containing peptides were isolated from fraction 5 by reversed-phase high-performance liquid chromatography on ODS-Hypersil. The cystine peptides were detected by differential chromatography of the non-reduced and the reduced samples. The primary structure of the peptides was solved by the Edman degradation reaction and by partial hydrolysis with thermolysin. Three peptides derive from the alpha 2- and beta-purothionins. The structure of the fourth peptide was determined as (Formula; see text) This sequence corresponds to positions 44-48 of known sequences of the high molecular weight (HMW) subunits 9, 10, and 12. Since Rektor contains the HMW subunits 9 and 10, it could be concluded that two HMW subunits 9 or 10, or one subunit 9 and one subunit 10 were linked parallel via two disulphide bridges.

Amino Acid Sequence↗

PubMed1988

Comparative investigations of partial amino acid sequences of prolamins and glutelins from cereals. VIII. Amino acid sequences of glutelin peptides.

The peptide fractions isolated from chymotryptic hydrolysates of wheat, rye and barley glutelins were separated by high-performance liquid chromatography on octadecyl silica gel. The peptides obtained were analysed for their amino acid composition and some also for their amino acid sequence. Characteristic sequences of peptides from wheat glutelin can be grouped into three types. The first type contains a high amount of Gly and frequently Tyr in the N-terminal positions. A typical partial sequence, which occurs repeated in two peptides, is QGQQPGQGQ. Sequences of this type are found in high-molecular-weight subunits. The second type is characterized by the sequence SQn (n = 3-5) followed by a hydrophobic tripeptide e.g., PPF, PVL; the most frequent sequence is SQQQQPPF. Low-molecular-weight subunits contain sequences of this type. The third type, which has partial sequences such as QQPQQPFP, corresponds to typical peptides from prolamin. Most sequences of peptides from rye and barley glutelins can be divided into two groups. The predominant type shows prolamin-like sequences, e.g., PQQPXPQQ with X being F or I. The second type is similar to glycine-rich peptides from wheat glutelin, except that repeating sequences are less frequent.

Amino Acid Sequence↗

PubMed1987

High-performance liquid chromatography of reduced glutenin: amino acid composition of fractions and components.

Reduced glutenin is separated by gel permeation high-performance liquid chromatography into three major and five minor fractions, which significantly differ in their amino acid compositions. By reversed-phase high performance liquid chromatography, about 20 glutenin components are obtained. These can be classified into three groups according to their amino acid compositions: a hydrophilic group with relatively high values of Glx and Phe, a more hydrophobic group with a high content of Gly, and a strongly hydrophobic group with higher values of Val and Leu. Groups 1, 2 and 3 contain middle-, high- and low-molecular-weight (MMW-, HMW-, LMW-) subunits respectively.

Amino Acids↗

PubMed1987

[Comparative study of partial amino acid sequences of prolamins and glutelins from various cereals. VII. Amino acid sequences of prolamin peptides].

The peptide fractions isolated from chymotryptic hydrolysates of wheat, rye and barley prolamines [this journal (1984) 178:173] were separated into pure peptides by high-performance liquid chromatography on octadecyl silica gel. The peptides which were most abundant were analyzed for amino acid composition and in part for amino acid sequence. Besides peptides which are typical for only one of the cereals investigated, peptides of similar composition were found in all three prolamines. These contain repeating sequences and are built up of mainly Gln (Q), Pro (P) and hydrophobic amino acids (X) such as Phe, Tyr, Ile, Val and Leu. One of the most frequent partial sequences is QQPQQPXP.

Amino Acid Sequence↗

PubMed1986

Coeliac activity of the gliadin peptides CT-1 and CT-2.

The coeliac active peptide B 3142, which has been isolated from a peptic-tryptic digest of gliadin and which consists of 53 amino-acid sequences, was partially hydrolyzed with alpha-chymotrypsin. The two fragment peptides CT-1 (positions 1-22 of B 3142) and CT-2 (positions 23-53) were separated by high-performance liquid chromatography on octadecyl silica gel and purified by gel filtration on Biogel P2. The examination in the organ-culture test including 18 coeliac patients on normal diet and 7 control persons have shown that the toxicity is preserved after the chymotryptic treatment and that the peptides B 3142, CT-1 and CT-2 do not significantly differ from one another according to their coeliac-specific effect.

Amino Acid Sequence↗

PubMed1984

[Comparative studies of partial amino acid sequences of prolamins and glutelins from various cereals. VI. Anion exchange chromatography of peptide fractions obtained by cation exchange chromatography].

The main peptide fractions obtained from prolamins and glutelins of wheat, rye, barley, and corn by chymotryptic hydrolysis, gel filtration and cation exchange chromatography [1, 2] were further separated by anion exchange chromatography. The amino-acid compositions of the peptides obtained from wheat, rye and barley prolamins are closely related. Typical compositions are Glx greater than 44, Pro greater than 28, and Phe greater than 7 mol-%. The peptide fractions from corn prolamine are different (Glx greater than 20, Leu greater than 20, Ala greater than 12, Pro greater than 10 mol-%). The peptide fractions from wheat, rye and barley glutelins are less similar. Typical compositions are Glx greater than 30, Pro greater than 15, and Gly greater than 8 mol-%. Most of the fractions from corn glutelin contain many amino-acids with Glx, Leu, and Ala predominating. Wheat differs significantly from the other cereals because of the unique composition of some high molecular weight peptide fractions from glutelin, which are rich in Glx (greater than 49) and Gly (greater than 19 mol-%).

Amino Acid Sequence↗

PubMed1984

Amino-acid sequence of the coeliac active gliadin peptide B 3142.

Peptide B 3142, which has been isolated from a peptic tryptic digest of whole gliadin by several separation steps [1], was examined for coeliac activity in an immunological test and in an organ-culture test, comparing enlarged groups of coeliac patients and control persons. In both test systems the peptide shows a coeliac specific effect. The N-terminal sequence analysis (EDMAN degradation), the C-terminal sequence analysis (incubation with carboxypeptidase Y) and the sequence determination of peptides, obtained from B 3142 by digestion with papain and chymotrypsin, result in the following total amino-acid sequence: H-Val-Pro-Val-Pro-Gln-Leu-Gln-Pro-Gln-Asn-Pro-Ser-Gln-Gln- Gln-Pro-Gln-Glu-Gln-Val-Pro-Leu-Val-Gln-Gln-Gln-Gln-Phe-Pro-Gly-Gln-Gln- Gln-Pro-Phe-Pro-Pro-Gln-Gln-Pro-Tyr-Pro-Gln-Pro-Gln-Pro-Phe-Pro-Ser-Gln- Gln-Pro-Tyr-OH. The 53 amino-acid residues correspond to a molecular mass of 6,129 g/mol.

Amino Acid Sequence↗

PubMed1983

[Chemical composition of seeds from Cucumeropsis mannii Naudin and their suitability as food].

Dehulled seeds from Cucumeropsis Mannii Naudin mainly consist of lipids (40.3%) and proteins (34.5%). Carbohydrates, minerals, and water amount to 16.5, 3.7, and 5.9%, resp. From this composition a caloric value of 2 190 kJ/100 g is calculated. The major component of the oil linoleic acid (57.9%). Short-chain fatty acids are absent. All important macro and micro nutrient elements are present in sufficient amounts for human nutrition. The seeds are rich in vitamin E and in niacin (30.8 mg/100 g and 14.3 mg/100 g. resp.). Consumption of 100 g dehulled seeds covers the daily requirement of essential fatty acids, vitamin E and essential amino acids--methionine excepted. Besides starch (14.3 g/100 g) sucrose (1.14 g/100 g), raffinose (0.42 g/100 g) and stachyose (0.41 g/100 g) as well as traces of glucose and fructose are present. The proteins extracted with various solvents (H2O, 0.1 M KCl-, 0.1 mM K3PO4-, and 0.5% SDS-solution) are studied by amino acid analysis. SDS-electrophoresis and isoelectric focusing. Molecular weights of these proteins are between 5,000 and 80,000 daltons with the fraction between 20,000 and 35,000 predominating. The seeds exhibit weak inhibition of trypsin and do not inhibit alpha-chymotrypsin.

Amino Acids↗

PubMed1983

Trihalogenated benzamides--a new class of artificial sweeteners.

2,4,6-tribromo-3-carboxyalkyl-benzamides and -carboxyalkoxy-benzamides are intensely sweet. With a recognition threshold value of about 1 mumol/l the 3-carboxyethyl compound is one of the sweetest compounds known. The intensity of the sweet taste depends upon the nature of the carboxyalkyl/carboxylalkoxy group. In respect to the acute toxicity to mice the compounds are similar to the sodium salt of saccharin and sodium cyclamate. The compounds are easily obtainable in good yield.

Animals↗