Studies on Desi and Kabull Chickpea (Cicer arietinum L.) Cultivars: Levels of Protease Inhibitors, Levels of Polyphenolic Compounds and in vitro Protein Digestibility

The levels of trypsin inhibitor activity were higher in both kabuli and desi seeds of chickpea than their chymotrypsin inhibitor activity. Mean values for the trypsin and chymotrypsin inhibitor units in dhal and seed samples of desi were higher as compared with kabuli cultivars. The presence of seed coat reduced the protein extraction. Mean values of polyphenolic compounds in seed samples of desi were more than twice that of kabuli and these differences disappeared in dhal samples indicating the distribution of these compounds mainly in the seed coat. The in vitro protein digestibility studies showed larger differences between desi seed and dhal samples when compared with kabuli seed and dhal samples. Polyphenolic compounds exhibited a highly significant and negative corretation (r = 0.872**) with in vitro digestibility of protein and a significant positive correlation with trypsin (r = 0.612*) and chymotrypsin (r = 0.507*) inhibitor activities.     

Natural plant enzyme inhibitors. Isolation of a trypsin/α-amylase inhibitor and a chymotrypsin/trypsin inhibitor from ragi (Eleusine coracana) grains by affinity chromatography and study of their properties

A trypsin/α-amylase inhibitor (TAI) and a chymotrypsin/trypsin inhibitor (CTI) were isolated in homogeneous forms from ragi grains by affinity chromatography using immobilised chymotrypsin and immobilised trypsin. Both the inhibitors were capable of inhibiting the caseinolytic and amidolytic activities of bovine trypsin whereas the esterolytic activity of the enzyme was only weakly affected. While TAI had no action on chymotrypsin, the CTI exerted an inhibitory effect on the caseinolytic activities of bovine α-, β-, γ- and ?-chymotrypsins. Both the inhibitors could inactivate the proteolytic actions of bovine as well as human crude pancreatic preparations, TAI showed inhibitory activity against human pancreatic, porcine pancreatic and human salivary amylase in the ratio of 6.5:5:1. The possible practical application of TAI for the purification of α-amylases by affinity chromatography is indicated based on the demonstration of the dissociation of porcine pancreatic amylase from a ‘trypsin-TAI-amylase’ trimer complex in the presence of maltose. The antichymotryptic activity of CTI was less stable than its antitryptic activity at high temperature, acidic pH and on treatment with pepsin. Modification of arginine residues by 1,2-cyclohexane dione led to a preferential inactivation of its antitryptic activity. Treatment of CTI with trinitrobenzene sulphonic acid or pronase, however, caused almost identical loss of both antitryptic and antichymotryptic activities. The mode of inhibition of CTI was non-competitive for trypsin but was uncompetitive for chymotrypsin. The CTI could bind to immobilised trypsin or chymotrypsin but not to immobilised TPCK-chymotrypsin or chymotrypsinogen.     

Characterisation of a trypsin/chymotrypsin inhibitor from jack fruit (Artocarpus integrifolia) seeds

Jack fruit seed (Artocarpus integrifolia Hook f) trypsin inhibitor (JSTI) was found to be rich in acidic amino acids and devoid of free thiol groups. The N-terminal and C-terminal amino acids of JSTI were aspartic acid and scrine, respectively. The inhibitor was stable under conditions of extremes of pH (3·0–12·0), at high temperatures and in the presence of denaturing agents. JSTI showed a non-competitive type of inhibition with K_i values of 0·48 ± 0·17 nM and 0·16 ± 0·04 nM for trypsin and chymotrypsin, respectively. The JSTI–trypsin complex exhibited chymotrypsin inhibitory activity suggesting the ‘double-headed’ nature of the inhibitor. Chemical modification of lysine residues resulted in loss of trypsin and chymotrypsin inhibitory activities of JSTI indicating that amino groups are essential for activity.     

Cooking quality and nutritional attributes of some nely developed cultivars of chickpea (Cicer arietinum)

Eight nely developed and to commonly gron chickpea (Cicer arietinum L) cultivars ere evaluated for their cooking quality by measuring cooking time, ater absorption and sensory properties. Nutritional aspects of cooked hole seed samples ere measured chemically (including amino acids and minerals) and biologically in nitrogen-balance experiments ith rats. Results indicated that kabuli (cream seed coat) may be generally preferred to desi (bron seed coat) cultivars in terms of cooking time and sensory properties. Calcium content as noticeably higher in desi than in kabuli cultivars, hereas magnesium, iron, copper and zinc shoed no definite trend. Levels of lysine, threonine, methionine and cystine of these genotypes ere ithin the range of FAO values. Desi and kabuli revealed no noticeable difference in protein and amino acids. Hoever, biological value as considerably higher for kabuli than for desi. Consequently, kabuli contained more utilisable protein and may be nutritionally better than desi. In general, cooking quality and nutritional aspects of both nely developed and control cultivars ere similar.     

Comparative physico-chemical studies on purified trypsin inhibitors from the endosperm of barley, rye, and wheat

The dominant trypsin inhibitors of the endosperm of barley, rye and wheat were investigated in a series of comparative studies. The barley and rye inhibitors showed a reaction of partial immunochemical identity, whereas no immunological cross-reactions between the wheat inhibitor and the inhibitors from barley and rye were detected. The molecular weight of the barley inhibitor is about 14,500, and of the rye and wheat inhibitors about 12,000. The three inhibitors had very similar amino acid compositions, but the wheat inhibitor seemed to contain nine disulfide bridges whereas the barley and rye inhibitor contain five and four, respectively. This may explain the higher stability of the wheat inhibitor towards proteolytic inactivation by pepsin and chymotrypsin. All three inhibitors were very stable to temperatures at 100 degrees C. The barley inhibitor was much less active against porcine trypsin, and especially human trypsin, than against bovine trypsin, whereas the inhibition by the rye and wheat inhibitor was less dependent on the origin of the enzyme.     

REACTION OF LENTIL PROTEINASE INHIBITORS WITH HUMAN AND BOVINE TRYPSIN AND CHYMOTRYPSIN1

The two main trypsin-chymotrypsin isoinhibitors previously purified from lentils (Lens culinaris Medik.), LCI-1 and LCI-4, inhibited one mol of human trypsin (1.05 and 1.00), more than one mol of bovine trypsin (1.53 and 1.38) and human chymotrypsin (1.70 and 1.43) as well as less than one mol of bovine chymotrypsin (0.62 and 0.54, respectively) per mol of inhibitor. Complex formation, together with chemical and enzymatic modification studies, showed that they were Bowman-Birk inhibitors with two independent reactive sites. One of these sites, mainly reacting with trypsin, contained arginine and bound tightly to bovine trypsin, less tightly to human trypsin and loosely to human chymotrypsin. The other reactive site, preferring chymotrypsin, contained tyrosine and bound tightly to human chymotrypsin, less tightly to bovine chymotrypsin and loosely to bovine trypsin. The amounts of bound enzyme exceeding one mol per mol of inhibitor reacted with the “wrong” sites: bovine trypsin with the chymotrypsin-reactive and human chymotrypsin with the trypsin-reactive one. The much higher inhibition of human chymotrypsin compared to that of bovine chymotrypsin resulted from a combination of two effects: the additional binding of human chymotrypsin at the “wrong” reactive site and the weak binding of the bovine chymotrypsin.     

Inhibitors of human and bovine trypsin and chymotrypsin in fenugreek (Trigonella foenum-graecum L.) seeds. Isolation and characterization

Three fenugreek inhibitors (TFI-A8, TFI-N2, and TFI-B2) were isolated from an inhibitor preparation by anion exchange chromatography and subsequent preparative isoelectric focusing using immobilized pH gradients and the canal technique. The purified inhibitors inhibited the enzymes tested differently: TFI-A8 exhibited a high inhibition of trypsin (8.2 mg human trypsin/mg and 8.1 mg bovine trypsin/mg) and a very low inhibition of chymotrypsin (0.8 mg human chymotrypsin/mg and 1.0 mg bovine chymotrypsin/mg). TFI-N2 inhibited the four enzymes to about the same extent (5.0 mg/mg human and 4.1 mg/mg bovine trypsin; 4.9 mg/mg human and 3.7 mg/mg bovine chymotrypsin). TFI-B2 displayed a high inhibition of trypsin (7.5 mg/mg human and 5.1 mg/mg bovine) and a low inhibition of chymotrypsin (1.8 mg/mg human and 1.9 mg/mg bovine). On average, the human enzymes were inhibited better than the bovine ones by the purified inhibitors. The inhibitors contained high amounts of cystine (five or six disulfide bridges per molecule), aspartic acid, threonine, serine and proline, no valine and methionine and two of them also no tryptophan. Their molecular masses were about 6 kDa. Their inclusion into the Bowman-Birk soybean proteinase inhibitor family is discussed.     

Inhibitors of human and bovine trypsin and chymotrypsin in fenugreek (Trigonella foenum-graecum L.) seeds. Reaction with the human and bovine proteinases.

The reaction between the three Bowman-Birk proteinase inhibitors isolated from fenugreek seeds (TFI-B2, TFI-N2 and TFI-A8) and the human and bovine proteinases was investigated by studying the complexes formed and their properties. TFI-B2, the Lys-Leu trypsin chymotrypsin inhibitor, can bind 1.9 mol human trypsin (HT), 1.3 mol bovine trypsin (BT) and/or 0.4 mol human (HCT) or bovine (BCT) chymotrypsin per mole of inhibitor. HT was bound at the two reactive sites and BT mainly at the lysine-containing trypsin-reactive site, whereas HCT and BCT were only bound at the leucine-containing chymotrypsin-reactive site. TFI-N2, the Arg-Leu trypsin chymotrypsin inhibitor, could bind 1 mol BT and BCT, but 1.3 mol HT and 1.2 mol HCT per mole of inhibitor. In addition to the usual binding, the human enzymes could also be bound at the respective "wrong" reactive site. TFI-A8, the Arg-Arg trypsin inhibitor, binds 2 mol HT or BT per mole of inhibitor at the two trypsin-reactive sites, whereas HCT and BCT (about 0.2 mol/mol) are bound to one of the two "wrong" reactive sites.     

A Method to Estimate the Hydration and Swelling Properties of Chickpeas (Cicer arietinum L.)

ABSTRACT:  Existing methodologies for estimating hydration properties in pulses (a potential indicator of cooking time) can be misleading and few measure both maximum hydration and the rate of hydration. Therefore, a new method, based on the Mitscherlich equation, was proposed and compared to existing methodologies. It was shown to be a superior estimator of both maximum hydration and hydration rate in desi and kabuli chickpeas. The new method was also superior for estimating maximum swelling and the rate of swelling in desi and kabuli chickpeas. Hydration and swelling data for 6 desi and 4 kabuli chickpea genotypes were compared using the new method and showed large genotypic differences. Use of the new method is recommended for estimating the hydration parameters of desi and kabuli chickpea for industry purposes and for selection of genotypes in breeding programs.     

Variability of Some Physico-chemical Characters in Desi and Kabuli Chickpea Types

A collection of 50 chickpea accessions (26 kabuli and 24 desi types) was evaluated for 2 years for eight physico-chemical seed characters: 100-seed weight, hydration capacity, hydration index, coat thickness and contents of protein, oil, acid detergent fibre (ADF) and starch. Significant differences were found between desi and kabuli types for the majority of the characters. The variance component due to the genotype×year interaction was important for the hydration index, starch and protein content, showing the importance of the year effect on genotypic expression of these characters. One kabuli accession and five desi accessions with high and stable protein content were selected. There was no overlap between the variation limits of desi and kabuli for coat thickness and ADF content. There were high positive and significant correlations between seed weight and oil content for both types of chickpea.     

Studies on Desi and Kabuli Chickpea (Cicer arietinum L.) Cultivars. The Levels of Amylase Inhibitors, Levels of Oligosaccharides and In Vitro Starch Digestibility

Amylase inhibitor activity (AIA) of chickpea extracts was investigated using pancreatic and salivary amylases. The extracts showed higher inhibitor activity towards pancreatic amylase than salivary amylase. Mean values indicated slightly higher inhibitory activity in desi than kabuli cultivars, though clear-cut differences were not observed among the cultivars. While in vitro starch digestibility of meal samples indicated no large differences among desi and kabuli types of chickpea, the mean values of digestibility of isolated starches of kabuli types was higher than those of desi types. The mean values of stachyose were higher in desi cultivars. When desi and kabuli types were considered together, stachyose and raffinose contents were not found significantly related to the concentrations of total soluble sugars while stachyose showed a significant correlation with raffinose.     

Characterisation of trypsin and α-chymotrypsin inhibitors in Australian wattle seed (Acacia victoriae Bentham)

Crude water extracts from Australian wattle seed (Acacia victoriae Bentham) and their salt (ammonium sulphate)-precipitated fractions were analysed for trypsin and α-chymotrypsin (chymotrypsin) inhibitor activity, using gel electrophoresis and spectrophotometric methods. Three different bands with molecular weight 30.20, 38.03 and 39.81 kDa were active, with the 50% salt-precipitated fraction exhibiting highest activity and number of active bands. The same proteins also appeared to be responsible for both trypsin and chymotrypsin inhibitor activity. To establish conditions for the inactivation of these inhibitors, whole seed and uncoated (dehulled) cotyledon were subjected to different heat treatments. Moist heat treatment at 100 °C for 30 s was sufficient to inactivate both protease inhibitors although the trypsin inhibitor was found to be more heat-resistant than was the chymotrypsin inhibitor. Soaking overnight, before thermal treatment, improved the trypsin inhibitor activity but enhanced the efficiency of thermal inactivation in both inhibitors.     

PARTIAL CHARACTERIZATION OF TRYPSIN-CHYMOTRYPSIN INHIBITORS FROM BEAN (PHASEOLUS VULGARIS L., VAR. ROSINHA G2): CHEMICAL AND PHYSICAL PROPERTIES

The three trypsin inhibitors A, B and C previously isolated from Brazilian pink bean (Phaseolus vulgaris L. var. Rosinha G2) had molecular weights of 18,200 to 18,500 by sodium dodecyl sulfate polyacrylamide gel electrophoresis, 20,000 by gel filtration on Sephadex G-100 and 20,400 by sucrose density gradient ultracentrifugation with a Stokes molecular radius of 20 Å, a frictional coefficient of 1.14, a diffusion coefficient of 10.7 × 10^?7 cm²s^?1, a partial specific volume of 0.69 cm³g^?1 and a molar absorptivity of 5.5 × 10³ M^?1 cm^?1 at 280 nm. All three inhibitors bound two moles of trypsin and one mole of chymotrypsin. The K_i values for trypsin were: A, 8.5 × 10^?10 M; B, 1.8 × 10^?10 M and C, 6.8 × 10^?10 M while for chymotrypsin they were: A, 4.4 × 10^?7 M; B, 2.8 × 10^?8 M and C, 3.0 × 10^?8 M. Reductive methylation caused loss of inhibitor activity of all three inhibitors against trypsin without significantly affecting inhibitor activity against chymotrypsin (with exception of inhibitor B), indicating that the inhibitors have lysine in binding site for trypsin. Partial reduction of the disulfide bonds caused loss of inhibitor activity against both trypsin and chymotrypsin with some regain of inhibitor activity following dialysis. Cyanogen bromide cleaved all three inhibitors into two fragments with significant retention of inhibitor activity. Cyanogen bromide-treated inhibitor B had nearly twice the original inhibitor activity against trypsin with no loss of inhibitor activity against chymotrypsin.     

Comparative studies on the inhibitory action of some legume seeds, potato tubers, and bran against human and bovine proteinases

Summary Inhibition of human trypsin and chymotrypsin by proteinase inhibitors of plant origin was studied using the juice from the small intestine, without separation of the two enzymes, and synthetic amide substrates (BAPA, GLUPHEPA). The results were compared with the inhibition of the corresponding bovine enzymes. Extracts and preparations from legumeseeds (13Papilionoideae, 2 Caesalpinioideae, 3Mimosoideae), potato tubers and bran were used as inhibitors; 9 of the seed extracts studied inhibited human chymotrypsin more and human trypsin less than the bovine enzymes. In similar tests 5 seed extracts inhibited the two human enzymes more than the bovine enzymes, whilst only one extract inhibited the two human enzymes less than the two bovine enzymes, and another inhibited human trypsin more and human chymotrypsin less than the bovine enzymes. In particular, human chymotrypsin was between two and twelve times as strongly inhibited as the bovine enzyme by some two thirds of the species studied, sometimes exhibiting chymotrypsin-inhibitory activities usually observed only with trypsin. Inhibitor preparations from the above legumes and two non-leguminous plant foods exhibited similar results.

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Vergleichende Untersuchung der Hemmwirkung von verschiedenen Leguminosensamen, Kartoffeln und Weizenkleie auf Human- und Rinderproteinasen

Zusammenfassung Die Hemmung von Trypsin und Chymotrypsin des Menschen durch verschiedene Proteinaseninhibitoren pflanzlicher Herkunft wurde unter Verwendung von Dünndarmsaft ohne Trennung der beiden Enzyme mit synthetischen Amidsubstraten (BAPA, GLUPHEPA) untersucht and mit der Hemmung der entsprechenden Rinderenzyme verglichen. Als Inhibitoren dienten Extrakte und Inhibitorpräpa-rate aus Leguminosensamen (13Papilionoideae, 2 Caesalpinioideae, 3Mimosoideae), Kartoffeln and Weizenkleie. Die Samenextrakte von 9 der untersuchten Leguminosenarten hemmen menschliches Chymotrypsin mehr und menschliches Trypsin weniger als die Rinderenzyme, 5 Samenextrakte hemmen beide Humanenzyme mehr als die Rinderenzyme, während nur ein Extrakt beide Humanenzyme weniger als die Rinderenzyme und ein weiterer Humantrypsin mehr and Humanchymotrypsin weniger hemmt. Humanchymotrypsin wird durch ungefähr zwei Drittel der untersuchten Arten zwischen zwei- bis zwölfmal so stark gehemmt wie das Rinderenzym. Die Hemmung von Chymotrypsin erreicht Werte, wie sie sonst nur für Trypsin bekannt sind. Inhibitorpräparate aus den untersuchten Leguminosen und aus zwei anderen pflanzlichen Lebensmitteln zeigen ähnliche Ergebnisse.

     

Natural plant enzyme inhibitors. Isolation and characterisation of a trypsin/chymotrypsin inhibitor from indian red wood (Adenanthera pavonia) seeds

A trypsin/chymotrypsin inhibitor was isolated from Indian red wood seeds by extraction with 0.01m HCl, chromatography on diethyl amino ethyl-cellulose, ammonium sulphate fractionation and gel chromatography on Sephadex G-100. The homogeneity of the final product was ascertained by affinity chromatography on trypsin sepharose and chromatography on phenyl sepharose CL-4B columns. During all stages of purification and characterisation the ratio of activities against trypsin and chymotrypsin remained constant at about 1.1:1 indicating that the same factor is responsible for both activities. The size of the inhibitor was found to be 24 000 daltons based on gel chromatographic studies on Sephadex G-100 and by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The molar ratio of interaction between the inhibitor and bovine trypsin for complete inactivation of the enzyme was found to be 1.04:1. Electrophoretic and gel chromatographic studies indicated that the purified inhibitor is capable of undergoing aggregation to form dimers and trimers. Even in the presence of sodium dodecyl sulphate and sodium dodecyl sulphateurea, this phenomenon was discernible. The binding sites on the inhibitor for trypsin and chymotrypsin were not mutually exclusive, based on the data from mixed enzyme studies and on analysis of the inhibitor-enzyme complexes by gel chromatography on Sephadex G-100. Modification of the arginyl residues of the inhibitor resulted in the loss of more of the antitryptic activity than of antichymotryptic activity. Conversely, modification of amino groups resulted in the loss of more of the antichymotryptic activity. The inhibitor was stable to exposure to a wide range of pH (1.0–12.0), but it was completely inactivated on heat-treatment at 100°C for 15 min. The mode of inhibition of trypsin as well as chymotrypsin was non-competitive and K_i values for the inhibitor were 2.92 × 10-¹⁰M and 4.46 × 10-¹⁰M , respectively, for the two enzymes.     

Purification of trypsin/chymotrypsin inhibitor from jack fruit seeds

A trypsin/chymotrypsin inhibitor (JSTI) was isolated from jack fruit seeds (Artocarpus integrifolia Hook f) by ammonium sulphate fractionation and chromatography on DEAE–cellulose and Sephadex G-100. During all stages of purification, the ratio of trypsin and chymotrypsin inhibitory activities remained constant. The purified preparation was found to be homogeneous by gel filtration, polyacrylamide gel electrophoresis (PAGE) and ultra-centrifugation. From the sedimentation coefficient, S _20w value of 3·5 ± 0·15 S. the molecular weight of JSTI was calculated to be 30·00 ± 2·50 kamu. The inhibitor showed a molecular weight of 24·55 kamu on a Sephadex G-75 column when eluted with 6 M guanidine hydrochloride, Under non-denaturing conditions, JSTI exhibited anomalous behaviour on a Sephadex G-200 column. On SDS–PAGE, the inhibitor showed two major bands with molecular weights of 26·30 and 15·00 kamu and two minor bands with molecular weights of 19·50 and 12·00 kamu. The carboxyamidomethylated JSTI showed three trypsin inhibitory activity bands on PAGE, suggesting the presence of isoinhibitors.     

Effects of extrusion and conventional processing methods on protein and antinutritional factor contents in pea seeds

The effects of high temperature short time (HTST) treatment compared with other conventional processes on protein, phytic acid, condensed tannins, polyphenols, trypsin, chymotrypsin and α-amylase inhibitor activities and haemagglutinating activities in Renata, Solara and Ballet pea seeds were investigated. Ballet cultivar showed highest protein, phytic acid, tannin, polyphenol contents and trypsin and chymotrypsin inhibitory activities. All pea cultivars contained trypsin- and chymotrypsin-inhibiting activity and lectins but only Solara had α-amylase inhibitory activity. Under extrusion conditions (148°C, 25% moisture and 100 rpm) this thermal processing method was the most effective in condensed tannin, trypsin, chymotrypsin, α-amylase inhibitors and haemagglutinating activity reduction, without modifying protein content as occurs by dehulling, soaking and germination treatments. Trypsin and chymotrypsin inhibitors and haemagglutinating activities in peas were more readily abolished by extrusion treatment than was chymotrypsin inhibitory activity.     

Characterisations of kabuli and desi chickpea starches cultivated in China

The characterisation of starches from kabuli and desi type chickpea seeds was investigated by monitoring amylose content, swelling power, solubility, synaeresis, water-binding capacity and turbidity properties. Total amylose and apparent amylsoe content were 31.80% and 29.93% for kabuli and 35.24% and 31.11% for desi, respectively. The shape of starch granules varied from round to oval or elliptic. The transition temperatures (T_o, T_p and T_c) were (62.237, 67.000 and 72.007 °C) and (59.396, 68.833 and 77.833 °C) for kabuli and desi starches, respectively. The ΔH value of kabuli type was higher than that of desi type. The crystal type of chickpea starches was a typical C_A-type pattern. Breakdown and setback viscosity of kabuli starch were lower than those of desi starch, indicating high heat and shear stability. Kabuli starch showed a higher value of M_w (5.382 × 10⁷ g/mol) than desi starch (3.536 × 10⁷ g/mol). Both kabuli and desi starches belonged to low glycaemic starches from measuring starch fractions and hydrolysis index.     

Natural plant enzyme inhibitors: A comparative study of the action of legume inhibitors on human and bovine pancreatic proteinases

Inhibition of total proteolytic (caseinolytic), tryptic (by hydrolysis of benzoyl arginine p-nitroanilide) and chymotrypic (by hydrolysis of acetyl tryosine ethyl ester) activities by ten species of legume seeds on human and bovine pancreatic proteases were compared. Sword bean extract had a negligible action on human enzymes, but could completely inhibit bovine trypsin and chymotrypsin. Indian red wood seed extract was more active on human than on bovine enzymes, whereas soya bean, field bean, kidney bean and bengal gram were more active on the bovine counterparts. While acacia seed extracts displayed more pronounced action on human trypsins and chymotrypsins, it was more effective in inhibiting the total proteolytic activity of the bovine system. Cowpea and red gram were more effective in inhibiting the human chymotrypsins. The relative contributions of trypsins plus chymotrypsins, elastases and carboxypeptidases to the total proteolytic activity of human pancreatic preparation were found to be 50, 25 and 25% whereas in the bovine system the values were 75, 20 and 5%.     

Subunit,amino acid composition and in vitro digestibility of protein isolates from Chinese kabuli and desi chickpea (Cicer arietinum L.) cultivars

The subunit, amino acid composition and in vitro digestibility of the two protein isolates (GCPI and ZCPI) from one kabuli and one desi chickpea cultivars, grown extensively in Xinjiang Autonomous Region of China, were investigated and compared with those of soy protein isolate (SPI). SDS–PAGE showed that GCPI and ZCPI had almost the same band components under the reduced and unreduced conditions, with only minor difference in relative quantity for some bands, but different from that of SPI. The sulphur-containing amino acids were the first limiting amino acids for all three protein isolates of GCPI (2.11 g/100 g), ZCPI (2.20 g/100 g) and SPI (1.99 g/100 g). Amino acid score of the three protein isolates could reach the FAO/WHO requirement (1990) for the essential amino acids for preschool children. The order of in vitro digestibility was GCPI (87.47%) > ZCPI (80.82%) > SPI (71.04%). Our results indicated that, compared with soybean protein isolate, Chinese kabuli and desi chickpea protein isolates had higher digestibility value, and chickpea protein, especially for kabuli protein, could be utilized as a good source of protein for human nutrition.