Synthesis, Preparation And Application Of Bioactive Peptides

Bioactive peptides have been defined as specific protein fragments that carry awide range of functional, biological and nutritionally properties. Functionally, thepeptides contribute to the sensory and physicochemical properties of various foods.Biologically, many dietary peptides have specific biological impact on bodyconditions and thus these components could be potential ingredients ofhealth-promoting or functional foods. Moreover, some biologically active peptides actas a source of amino acids and energy, which are essential for maintance and growth.Additionally, peptides have carried out an increasing role in the biomaterialnanotechnology, especially in the preparation of metal nanoparticles. Here,casein-derived phosphopeptides and ACE-inhibitory peptides as well as the precursorof aspartame (Z-APM) were obtained through peptide-bond cleavage and synthesismediated by protease. Furthermore, APM-AuNPs pocessing excellent catalyticactivity and electrochemical property, was prepared sucessfully. More details aredescribed as follows:1. The optimum conditions for the synthesis of Z-APM catalyzed by papain weredetermined, including the ratio of two phase (1:15), the concentration of triethylamine(1.0mmol/mL), temperature (40oC), the concentration of enzyme (4mg/mL forcrude-papain and1.6mg/mL for sigma-papain), the time consumed (72h forcrude-papain and18h for sigma-papain). Eventually, high yields of Z-APM wereobtained (26%for crude-papain and33%for sigma-papain).2. The mechanism of Z-APM synthesized by papain in the biphasic system wasanalyzed deeply. And the precipitate substance was identified as z-Asp-Phe-Phe-OMe.Based on the theory above, the fed-batch strategy was applied and higher yields ofZ-APM were achieved (44.5%for crude-papain and42%for sigma-papain).3. Having a large surface area and excellent mechanical property,CM-GLYMO-IDA-Ti4+exhibited significant advantages for the enrichment of CPPs.After enrichment, the purity of casein hydrolysate was improved suggested by HPLCprofiles. Meanwhile, the calcium-binding ability of CPPs increased significantlycompared with the hydrolysates. By means of infrared/fluorescence spectroscopy, weconcluded that it was mainly the phosphoserine cluster performing the calcium-chelating action for the10min-CPPs; while, for the other samples, carboxylgroups played an important role in calcium-binding capacity.4. Following casein hydrolysis by various proteases sequentially, a higher DHvalue (29.3%for pepsin+pancreatin+papain) was achieved, compared with thesingle enzymatic reaction (13.5%for pepsin,16.4%for pancreatin,20%for papain).Fractions A-F were obtained as a result of Sephadex G-25gel filtration and fraction Cwas found to exhibit the strongest ACE inhibitory activity (68.46%). Fraction C wasfurther separated by Sephadex G-15column and two fractions with higher activity(80%and94%) were collected.5. The microstructure and morphology of the as-prepared APM-AuNPs werecharacterized by microscopy as well as spectroscopy technologies. In terms ofapplication, APM-AuNPs showed good catalytic activity toward nitrophenolreduction. In addition, a high sensitivity could be obtained when the GC electrode wasmodified by APM-AuNPs.