Plant seeds contain a large number of protease inhibitors of animal, fungal, and bacterial origin. One of the well-studied families of these inhibitors is the Bowman-Birk family(BBI). The BBIs from dicotyledonous seeds are 8K, double-headed proteins. In contrast, the 8K inhibitors from monocotyledonous seeds are single headed. Monocots also have a 16K, double-headed inhibitor. We have determined the primary structure of a Bowman-Birk inhibitor from a dicot, horsegram, by sequential edman analysis of the intact protein and peptides derived from enzymatic and chemical cleavage. The 76-residue-long inhibitor is very similar to that of Macrotyloma axillare. An analysis of this inhibitor along with 26 other Bowman-Birk inhibitor domains (MW 8K) available in the SWISSPROT databank revealed that the proteins from monocots and dicots belong to related but distinct families. Inhibitors from monocots show larger variation in sequence. Sequence comparison shows that a crucial disulphide which connects the amino and carboxy termini of the active site loop is lost in monocots. The loss of a reactive site in monocots seems to be correlated to this. However, it appears that this disulphide is not absolutely essential for retention of inhibitory function. Our analysis suggests that gene duplication leading to a 16K inhibitor in monocots has occurred, probably after the divergence of monocots and dicots, and also after the loss of second reactive site in monocots.
Four proteinase inhibitors were purified to homogeneity from horse gram (Dolichos biflorus). These inhibitors are double‐headed and inhibit trypsin and chymotrypsin simultaneously and independently. Dissociation constants range between 0.87 and 4.6 × 10−7 M. Each of the four isoinhibitors possesses a crucial lysine residue at the trypsin reactive site. These inhibitors have molecular masses of 8.5 kDa and isoelectric points of 4.6 to 5.6. They exist mainly as dimers under physiological conditions. Amino acid analysis revealed high levels of half‐cystine, serine, aspartate and proline but low levels of methionine and aromatic amino acids. Amino‐terminal sequence analysis revealed that each of the four isoinhibitors have a conserved core sequence but are divergent at the N‐terminal end. These inhibitors belong to the Bowman‐Birk (BBI) family of proteinase inhibitors as reflected by their inhibitory properties, amino acid composition and homology to other BBIs.
Green gram legume cultivars were analyzed for their protein solubility profile by fractionation in the raw form and also after heat processing. The results indicated that globulin fractions, which are present in major amounts that ranged from 79.5 to 85.4 % significantly decreased after the heat treatment. This decrease was accompanied by a significant increase in the glutelin-3 fractions. The prolamine contents did not vary considerably after processing. The protein and non-protein nitrogen contents ranged from 22.6 to 26.2 % and 2.3 to 2.7 % in the legume cultivars, respectively. The antinutritional factors like total polyphenol and phytic phosphorous were also determined. The accumulation of polyphenols was in the seed coat portion of the legume where as that of phytic phosphorus was in the cotyledons. SDS -PAGE profiles of all the three green gram cultivars had five major polypeptides (molecular weight 15, 18, 20, 45 and 60 kDa) in the total protein composition. Wide variation in electrophoresis pattern was observed after heat processing. Thermal treatment increased the insoluble protein fractions and eliminated the minor polypeptide bands below 14.3 kDa in the green gram cultivars.
The physicochemical characteristics and minor component contents of blended oils packed in pouches in relation to starting oils used for blending were studied over a period of 6 mon at two storage temperatures and humidity conditions: 27°C/65% RH and 40°C/30-40% RH. Color, PV, FFA value, β-carotene content, tocopherol content, and oryzanol content of the oils were monitored at regular intervals. The color, PV (0.6-20.7 meq O 2 /kg , FFA value (0.08-2.1%), tocopherol content (360-1700 ppm%), oryzanol content (460-2,000 mg%), and sesame oil antioxidants (400-2,000 mg%) were not changed in either the starting oils or their blends. Oils and oil blends containing a higher initial PV (18.9-20.7 meq O 2 /kg) showed a slight reduction in value at 40°C, whereas oils having lesser PV of 5-10 showed a slight increase during the storage period. Among the minor components studied, only β-carotene showed a reduction, 8.9-60.2% at 27°C and 48-71% at 40°C, for the different oil blends studied. The observed results indicated that the packed oil blends studied were stable under the conditions of the study, and the minor components, other than β-carotene, remained unaltered in the package even at the end of 6 mon of storage.
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