ABSTRACT
This study was aimed to optimize the hydrolysis conditions of Coix prolamin, which occupied the highest content in total protein of it, and then evaluate the angiotensin-converting enzyme (ACE) inhibitory activity of the corresponding hydrolysates. Pepsin was used to hydrolyze prolamin and OPA method was applied to determine the degree of hydrolysis. The optimum conditions of hydrolyzing prolamin were obtained by orthogonal design subse-quently. The ACE inhibitory activity of small molecular weight (less than 3 kD) peptides gained by ultrafiltration of the hydrolysates was assayed by RP-HPLC method. The result showed that the optimized hydrolysis conditions were substrate concentration of 1%, enzyme-to-substrate ratio of 1:5 and hydrolysis duration for 48 h. The hydrolysates exhibited an ACE inhibitory ratio of (83.40 ± 0.93)% at the concentration of 0.1 mg·mL-1. It was concluded that prolamin hydrolysates displayed a high ACE inhibitory activity in vitro, which provided guidance for further research of antihypertensive component and development of functional food from Coix.
ABSTRACT
The isolation procedure of the seed proteins of Amaranthus blitum have been analyzed at different pH conditions. Qualitative studies were carried out by using electrophoretic technique sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Mainly four protein fractions i.e. albumin, globulin, prolamin and glutelin were obtained. Protein isolates were prepared by (a) extraction at different alkaline pH (9, 10, 11 and 12) and precipitation at pH 5 and (b) extraction at pH 9 and precipitation at different pH (4, 5, 6 and 7). The composition of isolates, prepared by method (a), depended on extraction pH. The isolate extracted at pH 8 was mainly composed of albumin and globulin, whereas at pH 9, 10 and 11 showed the presence of prolamin and glutelin. Electrophoretic pattern of different isolates had five major bands with molecular weight of 30, 45, 72, 84 and 90 kDt respectively. The increase of the extraction pH led to the increase in protein yield. With method (b) isolates obtained were variable in composition. At pH 7 albumin and prolamine were present, whereas at pH 4, 5 and 6 all 4 protein fractions were precipitated. According to the quantitative estimation of the albumin, globulin, prolamin and glutelin in the seed flour the contents were 26.4, 25, 5.81 and 42.7%, respectively. The results suggest that composition of protein isolates could be controlled by different extraction and precipitation pH.
ABSTRACT
Food allergy is an adverse food reaction as a result of immune mechanisms. In a sensitized individual, food allergens activate mast cells and basophils by binding with IgE present on the cell surface, resulting in the release of chemical mediators and various cytokines to cause various clinical symptoms of food allergy. Sensitization to food allergens can occur in the gastrointestinal tract (class 1 food allergy) or as a consequence of cross reactivity to structurally homologous inhalant allergens (class 2 food allergy). The class 1 food allergens are water-soluble glycoproteins with 10-70 kD size that are resistant to heat, acid and enzymes. On the other hand, the class 2 food allergens are highly unstable and degraded by heat or enzymatic digestion. Much progress has been made in identifying and isolating food allergen. Recently cDNAs for many proteins have been isolated and recombinant proteins have been generated. These techniques make it easier to characterize each responsible food allergens. Plant food allergens are classified into families and superfamilies by their structural and functional properties. The most of plant food allergens are the cupin and prolamin superfamilies and the protein families of the plant defense system. The cupin superfamily includes allergenic seed storage proteins of 7s globulin (vicilin) and 11s globulin (legumin). 2s albumin seed storage proteins, the nonspecific lipid transfer proteins, and the cereal alpha-amylase and protease inhibitors belong to the prolamin superfamily. Profilins, heveins, and nonspecific lipid transfer proteins are present in a variety of pollens, nuts, seeds, fruits, and vegetables. These are considered as panallergens, causing a significant degree of IgE-mediated cross-reactivity. Detailed informations about the character of food allergens can be used to develop more sophisticated diagnostic methods and treatment modalities in the near future. Further knowledge of food allergens is also useful to assess the allergenicity of novel protein of genetically mo.