|摘要: ||本研究由黑腹虎頭蜂 (Vespa basalis) 毒液中分離出的小型胜肽mastoparan-B (MP-B)，探討其生物活性，包括抗氧化性 (antioxidative activities)、抗菌性 (antimicrobial activities)、溶血性 (hemolytic activities) 以及促進肥大細胞去顆粒化之活性 (mast cell degranulation, MCD)，並將其特定胺基酸取代，研究所得衍生物之活性變化。試驗結果顯示MP-B具有良好之抗菌性，在小於8 μg/mL劑量的情形下，對大腸桿菌 (Escherichia coli) 之BL21及JM109AmpR兩種品系、木糖葡萄球菌 (Staphylococcus xylosus)、克氏檸檬酸桿菌 (Citrobacter koseri) 等有良好的抑菌殺菌活性，並且對革藍氏陽性及陰性菌種無偏好性，在128 μg/mL測試濃度下，對維持腸道健康的腸道益生菌沒有明顯影響，並且對紅血球之溶血性和促進肥大細胞去顆粒化之活性亦不顯著；此外在8-16 μg/mL低劑量的情形下，MP-B具有與一氧化氮 (nitric-oxide, NO) 競爭氧分子 (oxygen molecules, O2) 的良好抗氧化活性，及類似超氧歧化酶 (superoxidase dismutase, SOD) 和麩胱甘肽過氧化酶 (glutathione peroxidase, GPx) 之活性。經由特定胺基酸取代之方式，使MP-B之疏水性改變所得之衍生物確實可以提昇MP-B之抗氧化性及抗菌性。其中一個衍生物MP-B-1，藉由將MP-B第三個胺基酸由白胺酸 (leucine, Leu) 取代成色胺酸 (tryptophan, Trp)，其對試驗菌株之抑菌殺菌活性有顯著增加，尤其針對克雷伯氏菌 (Klebsiella pneumonias)、沙門氏桿菌 (Salmonella typhimurium) 以及沙門氏豬霍亂桿菌 (Salmonella Choleraesuis)之活性甚至增加八倍之多；而在抗氧化性上，包括還原力 (reducing power)、DPPH自由基清除率 (DPPH scavenging activity) 以及類似麩胱甘肽還原酶 (glutathione reductase, GRd) 之活性均有顯著之增加；而另兩個衍生物之活性變化，MP-B-2大多為持平，MP-B-3則大多為大幅下降。另外隨著試驗劑量的升高，衍生物對腸道益生菌和紅血球之溶血活性並無顯著之影響，但對肥大細胞去顆粒化之活性顯著上升。因此，適當的胺基酸取代方式，並控制可能對腸道益生菌、紅血球以及肥大細胞產生之毒性影響，將使得MP-B和其衍生物未來在抗菌及抗氧化之應用上極具潛力。|
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.