Abstract:The water soluble total protein (TP) of selenium-enriched Spirulina platensis (SeSP), named as SeSP-TP, was extracted by phosphate buffer and then hydrolyzed by 5 different proteases to produce SeSP peptides (SeSP-Ps). The angiotensin-converting enzyme (ACE) inhibitory activity of SeSP-Ps was measured in vitro and ICP method was used to rapidly determinate of selenium in algae powder and total protein content. The results showed that treatments with different proteases caused different degree of hydrolysis (DH) of SeSP-TP, and the combination digestion by pepsin, trypsin and chimotrypsin led to the highest DH value. The SeSP-Ps obtained via hydrolysis by the combination digestion of pepsin, trypsin and chimotrypsin showed the highest ACE-inhibitory activity (89.47%). The ACE inhibition efficiency of polypeptides prepared by alkaline protease is higher. Fluorescence detection showed that, when the content of selenium peptides was above 50 mu g/mL, the synthesis of NO was obviously promoted. However, selenium protein showed little effect on the reaction.Selenium contents in both water-soluble and water-insoluble components accounted for 95.47% of total selenium, probably due to that in extraction and preparation of SeSP-TP, some selenium protein and small molecules containing selenium missed in precipitation, dissolution and dialysis steps.
