Study On Bactericidal Activity Of Thymopentin Peptide And Its Derived Peptides

OBJECTIVE:To study the bactericidal activity of Thymopentin peptide and its derived peptides in vitro and to understand the relationship between structure and bactericidal activity of Thymopentin.METHODS:According to the amino acid sequence of Thymopentin,six peptides were synthesized respectively as fellow:?Thymopentin,the amino acid sequence was Arginine-Lysine-Aspartic acid-Valine-Tyrosine(RKDVY,referred to as RKD5);? The derived peptide one was one of the acidic amino acid-Aspartic acid(D)of Thymopentin substituted by neutral amino acid-Asparagine(N),the sequence was Arginine-Lysine-Asparagine-Valine-Tyrosine(RKNVY,referred to as RKN5);?The derived peptide two was one of the acidic amino acid-Aspartic acid(D)was substituted by basic amino acid-Lysine(K)of Thymopentin,the sequence was Arginine-Lysine-Lysine-Valine-Tyrosine(RKKVY,referred to as RKK5);? The derived peptide three was join a sequence of Thymopentin behind the sequence of Thymopentin,the sequence was Arginine-Lysine-Aspartic acid-Valine-Tyrosine—Arginine-Lysine-Aspartic acid-Valine-Tyrosine(RKDVYRKDVY,referred to as RKD10);? The derived peptide four was add two proline in amino acid sequence of derived peptide three,the sequence was Arginine-Lysine-Aspartic acid-Valine-Tyrosine-Proline-Tyrosine-Valine-Aspartic acid-Lysine-Arginine-Proline(RKDVYPYVDKRP,referred to as RKD12);? The derived peptide five was modified to ring from derived peptide four,the sequence was RKDVYPYVDKRP ring(referred to as RKD12ring).The bactericidal activity was determined by agar plating-method.Six strains of bacterial,Gram negative bacteria(G-)Proteusbacillus vulgaris,Escherichia coli,Pseudomonasaeruginosa,Gram positive bacteria(G+)Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis,were incubated with different concentration of derived peptides at 37 ? for 2 hours in a water bath respectively.Then the reaction solution was diluted and agar plates were poured.After 18-24 hours incubation in the thermostated container at 37 ?.The colony formedunits were countedandthe bactericidal rates were calculated.RESULTS:?The thymopentin and derived peptides RKD5,RKN5,RKK5 possessed bactericidal activity against Gram positive bacteria(G+)Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis,the activity from strong to weak was RKK5>RKN5>RKD5;they possessed bactericidal activity against Gram negative bacteria(G-)Proteusbacillus vulgaris,Escherichia coli,Pseudomonas aeruginosa.The bactericidal activities of RKK5,RKN5 were stronger than RKDs,there was no significant different between RKK5 and RKN5;? The two derived peptides RKD10 and RKD,2,possessed bactericidal activity against Gram positive bacterna(G+)Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis and Gram negative bacteria(G-)Proteus bacillus vulgaris,Escherichia coli,Pseudomonas aeruginosa.The,activities of RKD12 was stronger than RKD10;?The Derived peptides RKDi2ring has no significant bactericidal activities against Gram positive bacteria(G+)Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis and Gram negative bacteria(G-)Proteusbacillus vulgaris,Escherichia coli,Pseudomonas aeruginosa.CONCLUSION:? Thymopentin RKD5 possessed bactericidal activity against the common Gram positive bacteria(G+)Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis and Gram negative bacteria(G-)Proteusbacillus vulgaris,Escherichia coli,Pseudomonas aeruginosa.? It's derived peptides RKN5,RKK5,RKD10 and RKD12 possessed bactericidal activity against the common Gram positive bacteria(G+)Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis and Gram negative bacteria(G-)Proteusbacillus vulgaris,Escherichia coli,Pseudomonas aeruginosa in clinic.The Derived peptides RKD12ring has no significant bactericidal activities against the common Gram positive(G+)bacteria Staphylococcus aureus,Enterococcus faecium,Bacillus subtilis and Gram negative(G-)bacteria Proteusbacillus vulgaris,Escherichia coli,Pseudomonas aeruginosa in clinic.? The thymopentin and derived peptides's bactericidal activity is related to positive net charge,amphiphilic,hydrophobicity,may also related to its molecular weight,isoelectric point,the spatial structure of the peptide molecular and difference between bacterial cell membranes.