Study On Antioxidant And Antihypertensive Activities Of Two Kind Of Red Algal Peptides

Porphyra haitanensis and Gracilaria lemaneiformis are two important economic algae widely cultivated in coastal areas of China.The two algae are rich in nutrients for edible and medicinal purposes,especially P.haitanensis,which has the same amount of protein as terrestrial plant soybeans and is rich in essential amino acids.In this paper,the preparation of enzymatic peptides from P.haitanensis and G.lemaneiformis and the anti-oxidation and angiotensin-converting enzyme?ACE?inhibitory activities were studied.1.Two ACE inhibitory peptides with specific sequences were identified by LC-MS/MS in the enzymatic hydrolysis peptide solution of trypsin of G.lemaneiformis??3kDa?.The IC₅₀ values for FQIN[M?O?]CILR and TGAPCR were determined to be9.64±0.36?M and 23.94±0.82?M,respectively.Both peptides are temperature and pH stable and maintain structural stability and mimic ACE inhibition in simulated gastrointestinal fluids.Enzymatic kinetic studies revealed that the two peptides are non-competitive inhibitors of ACE.Molecular docking simulations revealed that two peptides interfere with ACE by forming hydrogen bonds with key amino acid residues associated with the ACE-catalyzed substrate.In addition,both peptides still exert significant antihypertensive activity in SHR,both of which significantly reduce SHR systolic blood pressure?SBP?and diastolic blood pressure?DBP?.Among them,FQIN[M?O?]CILR can exert better antihypertensive effect in SHR than TGAPCR.2.Compare the traditional extraction methods of the laboratory and the effect of enzymatic method on the protein extraction in the P.haitanensis.By comparison,the ultrasonic extraction method is still an efficient and economical method for extracting P.haitanensis protein.Secondly,cellulase can destroy the structure of the cell wall of seaweed and promote the dissolution of intracellular proteins.3.The antioxidant activity and ACE inhibitory activity of the enzymatic peptides of P.haitanensis were investigated.The enzymatic hydrolysate of each protease has certain antioxidant activity,and the component with molecular weight?1 kDa can exert better antioxidant activity than the component with molecular weight?1 kDa.Among the enzymatic peptides of the five proteases,the enzymatic hydrolysis of the peptide of the neutral protease and trypsin showed better comprehensive antioxidant capacity.Only a part of the peptides obtained by enzymatic hydrolysis of each protease have ACE inhibitory activity.The active center of ACE has a certain spatial structure.Therefore,a peptide having a molecular weight of?1 kDa can be inserted into an ACE active site,interfere with the ACE-catalyzed substrate,and exert an inhibitory activity.Among the enzymatically hydrolyzed peptides of the five proteases,trypsin and alkaline protease showed good ACE inhibitory activity.Therefore,in the further screening of the bioactive peptide of P.haitanensis,trypsin or alkaline protease or a combination of the two can be used to prepare the ACE inhibitory peptide.