酚氧化酶原在蜜蜂体内的分布及其特性研究

Distribution and characterization of prophenoloxidase(PPO)of honey bee(Apis mellifera)

酚氧化酶(PO)是一种含铜氧化酶,在黑色素的合成及抵抗病毒感染的免疫反应中起着重要作用,在昆虫体内主要以酚氧化酶原(PPO)的形式存在于血淋巴中。蜜蜂在不同发育阶段的PPO转录本水平已有报道,但对影响PO活性的研究较少。本研究调查了PPO在工蜂与蜂王组织中的分布,发现AmPPO在工蜂和蜂王的各种组织中都有分布。但与蜂王相比,AmPPO在工蜂各组织(头、胸、表皮、足、翅、中肠、血淋巴、气管、卵巢)的转录本含量比蜂王相应组织中都高。金属离子对PO活性的影响结果表明,Ca^(2+)或Mg^(2+)均会降低PO活性,Cu^(2+)对PO的活性没有影响。然而,Cu^(2+)与Mg^(2+)或Ca^(2+)结合会显著提高PO活性(P<0.05)。此外,我们还确定了PO的最适pH和温度分别为5.5和36℃。本研究为进一步研究蜜蜂对病害的免疫反应提供了数据。

Phenoloxidase(PO)is a copper-containing oxidase,which plays an important role in melanin synthesis and defenses against pathogenic microorganisms.It exists in hemolymph as a form of precursor,prophenoloxidase(PPO),before it is hydrolyzed.The expression level of AmPPO at different development stage of honey bee had been reported but the factors infl uencing the PO activity are less known.Here,we found that AmPPO was distributed in various tissues of worker bees and queen.Compared with the queen,however,AmPPO had a significantly higher expression level in various tissues of worker bees including head,thorax,cuticle,leg,wing,midgut,hemolymph,trachea and ovary.The effect of different metal ion on PO activity was evaluated and showed that both Ca^(2+)and Mg^(2+)will reduce the PO activity,but not for the copper ion.However,the combination of Cu^(2+)and Mg^(2+)or Ca^(2+)will signifi cantly increase PO activity(P<0.05).In addition,we confi rmed the optimal pH and temperature of PO were 5.5 and 36℃ respectively.Our studies provided useful information for further studying host immune response involved in against pathogens of honey bee.