| Summary: | 博士 === 國立中興大學 === 昆蟲學系所 === 101 === This study evaluated antimicrobial activities, antioxidative activities, hemolytic activities and mast cell degranulation of mastoparan-B (MP-B) isolated from the venom of the hornet, Vespa basalis, and its analogs after substituting certain amino acid (aa) residues. MP-B exhibited significantly different antimicrobial activities against bacteria species/strains tested, especially Escherichia coli BL21 and JM109AmpR, Staphylococcus xylosus and Citrobacter koseri at low dosages (< 8 μg/mL), and was non-specific against certain Gram-positive and -negative bacteria. MP-B was not effective against the beneficial probiotics, hemolytic to erythrocytes, and no predominant rates of mast cell degranulation at the dosages tested (128 μg/mL). MP-B is a novel, valuable antioxidant at low concentrations (8-16 μg/mL) in competing with nitric oxide for oxygen molecules and possesses highly antioxidative enzyme activities resembled to superoxidase dismutase and glutathione peroxidase. Our results indicated that hydrophobicity modification by single aa substitution may enhance their antimicrobial activities and antioxidative activities. An aa substituted MP-B, viz., MP-B-1, in which Trp substituted for Leu3, became more effective than the original peptide in inhibiting or killing the bacterial species tested, especially Klebsiella pneumonia, Salmonella typhimurium, and Salmonella Cholerasuis, even up to 8 times more effective than MP-B in some cases. Antioxidative activities of MP-B-1, including the reducing power, DPPH scavenging activity and glutathione reductase-like enzyme activity, were also increased. However, MP-B-2 was virtually similar to the activities of MP-B, while MP-B-3 reduced greatly its effectiveness compared to others. On the other hand, the analogs were not effective against the beneficial probiotics and not hemolytic to erythrocytes at the dosages tested, but there are clearly increasing rates of mast cell degranulation. Therefore, it is suggested that MP-B could be more potent against specific pathogenic bacteria as well as safer to mast cells after undergoing appropriate amino acid substitutions, and is potential to be applicable antioxidants for antioxidative application.
|
|---|
