Department of Molecular Medicine, Faculty of Medicine, CENAR, University of Malaya, Kuala Lumpur, Malaysia.
Comp Biochem Physiol C Toxicol Pharmacol. 2011 Mar;153(2):237-42. doi: 10.1016/j.cbpc.2010.11.001. Epub 2010 Nov 6.
The major l-amino acid oxidase (LAAO, EC 1.4.3.2) of king cobra (Ophiophagus hannah) venom is known to be an unusual form of snake venom LAAO as it possesses unique structural features and unusual thermal stability. The antibacterial effects of king cobra venom LAAO were tested against several strains of clinical isolates including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli using broth microdilution assay. For comparison, the antibacterial effects of several antibiotics (cefotaxime, kanamycin, tetracycline, vancomycin and penicillin) were also examined using the same conditions. King cobra venom LAAO was very effective in inhibiting the two Gram-positive bacteria (S. aureus and S. epidermidis) tested, with minimum inhibitory concentration (MIC) of 0.78μg/mL (0.006μM) and 1.56μg/mL (0.012μM) against S. aureus and S. epidermidis, respectively. The MICs are comparable to the MICs of the antibiotics tested, on a weight basis. However, the LAAO was only moderately effective against three Gram-negative bacteria tested (P. aeruginosa, K. pneumoniae and E. coli), with MIC ranges from 25 to 50μg/mL (0.2-0.4μM). Catalase at the concentration of 1mg/mL abolished the antibacterial effect of LAAO, indicating that the antibacterial effect of the enzyme involves generation of hydrogen peroxide. Binding studies indicated that king cobra venom LAAO binds strongly to the Gram-positive S. aureus and S. epidermidis, but less strongly to the Gram-negative E. coli and P. aeruginosa, indicating that specific binding to bacteria is important for the potent antibacterial activity of the enzyme.
眼镜王蛇（Ophiophagus hannah）毒液中的主要 L-氨基酸氧化酶（LAAO，EC 1.4.3.2）是一种不寻常的蛇毒 LAAO，因为它具有独特的结构特征和不寻常的热稳定性。使用肉汤微量稀释测定法，测试了眼镜王蛇毒液 LAAO 对包括金黄色葡萄球菌、表皮葡萄球菌、铜绿假单胞菌、肺炎克雷伯菌和大肠杆菌在内的几种临床分离株的抗菌作用。为了比较，还使用相同条件测试了几种抗生素（头孢噻肟、卡那霉素、四环素、万古霉素和青霉素）的抗菌作用。
眼镜王蛇毒液 LAAO 对测试的两种革兰氏阳性菌（金黄色葡萄球菌和表皮葡萄球菌）非常有效，对金黄色葡萄球菌和表皮葡萄球菌的最小抑菌浓度（MIC）分别为 0.78μg/mL（0.006μM）和 1.56μg/mL（0.012μM）。MIC 与测试抗生素的 MIC 相当，按重量计算。然而，LAAO 对测试的三种革兰氏阴性菌（铜绿假单胞菌、肺炎克雷伯菌和大肠杆菌）只有中度的效果，MIC 范围从 25 到 50μg/mL（0.2-0.4μM）。浓度为 1mg/mL 的过氧化氢酶消除了 LAAO 的抗菌作用，表明该酶的抗菌作用涉及过氧化氢的产生。结合研究表明，眼镜王蛇毒液 LAAO 强烈结合革兰氏阳性菌金黄色葡萄球菌和表皮葡萄球菌，但与革兰氏阴性菌大肠杆菌和铜绿假单胞菌的结合较弱，表明与细菌的特异性结合对于该酶的强抗菌活性很重要。
