Design of Oxidative Capacities in Hymenopteran Flight Muscles

在动物界，飞虫的有氧代谢率是已知最高的。这些高代谢通量率是如何实现以支持飞行的尚不清楚。在飞行过程中，稳态的机械功速率决定了ATP水解和再合成的速率。申请人询问ATP合成能力与飞行所需ATP的关系。在以前使用蜜蜂（Apis mellifera）进行的研究中，申请人发现在飞行过程中糖酵解酶的能力和糖酵解率之间存在非常密切的匹配。作为这些研究的延伸，将进行进一步的研究，以确定线粒体氧化能力与飞行过程中需求的匹配程度。一个重要的问题是，蜜蜂飞行肌线粒体是否比脊椎动物的恒温肌肉线粒体具有更高的呼吸和氧化磷酸化能力。蜜蜂线粒体将被分离和表征，以确定氧化能力如何与飞行中达到的呼吸速率相关。进一步研究蜜蜂高呼吸速率的基础将涉及对分离肌肉线粒体中电子转移反应的机制研究。生物化学能力与生理通量率之间的关系将在不同种类的兰花蜜蜂的比较研究中进一步探讨，这些蜜蜂的大小差异很大，并且已知在飞行过程中体重与质量特异性代谢率之间表现出反比关系。研究人员提出，在eugineine蜜蜂中，体重与质量特异性有氧代谢率之间的反比关系部分是通过线粒体含量和结构的变化以及随着体重下降而提高的酶周转率（每个酶分子的电子传递率）来实现的。这些独特的研究将阐明代谢酶如何在体内发挥作用以及控制生化能力设计的原则。人们对多少酶是“足够而不是太多”的规则知之甚少。申请人的研究计划是基于这样一种信念，即朝着这一目标的进展对生物学至关重要。

Flying insects achieve the highest known mass-specific rates of aerobic metabolism in the Animal Kingdom. How these high metabolic flux rates are achieved to support flight is poorly understood. During flight, steady state rates of mechanical work define rates of ATP hydrolysis and resynthesis. The applicant asks how capacities for ATP synthesis are related to ATP requirements for flight. In previous studies using honeybees (Apis mellifera), the applicant found remarkably close matches between enzymatic capacities for glycolysis and glycolytic rates achieved during flight. As an extension of these studies, further research will beconducted to determine how closely mitochondrial oxidative capacities match requirements during flight. An important question is whether honeybee flight muscle mitochondria possess inherently higher capacities for respiration and oxidative phosphorylation than mitochondria from vertebrate homeotherm muscles. Honeybee mitochondria will be isolated and characterized to determine how oxidative capacities are related to the respiration rates achieved in flight. Further studies to investigate the basis for high respiration rates in honeybees will involve mechanistic studies of electron transfer reactions in isolated muscle mitochondria.The relationships between biochemical capacities and physiological flux rates will be further explored in a comparative study using various species of Euglossine (orchid) bees, which vary greatly in size and are known to display an inverse relationship between body mass and mass-specific metabolic rate during flight. It is proposed that in Euglossine bees, the inverse relationship between body mass and mass-specific aerobic metabolic rate is achieved partly through variation in mitochondrial content and structure, as well as higher enzyme turnover rates (electron transfer rate per enzyme molecule) with declining body mass. These unique studies will shed light upon how metabolic enzymes function in vivo and the principles governing the design of biochemical capacities. The rules that govern how much enzyme is "enough but not too much" are poorly understood. The applicant's research program is based on the belief that progress towards this goal is of fundamental importance to biology.