Jue Thomas, Simond Gregory, Wright Traver J, Shih Lifan, Chung Youngran, Sriram Renuka, Kreutzer Ulrike, Davis Randall W
Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, CA, 95616-8635, USA.
Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX, 77843, USA.
J Physiol Biochem. 2016 Aug;73(3):359-370. doi: 10.1007/s13105-017-0559-z. Epub 2017 Mar 29.
Recent studies have suggested myoglobin (Mb) may have other cellular functions in addition to storing and transporting O. Indeed, NMR experiments have shown that the saturated fatty acid (FA) palmitate (PA) can interact with myoglobin (Mb) in its ligated state (MbCO and MbCN) but does not interact with Mb in its deoxygenated state. The observation has led to the hypothesis that Mb can also serve as a fatty acid transporter. The present study further investigates fatty acid interaction with the physiological states of Mb using the more soluble but unsaturated fatty acid, oleic acid (OA). OA binds to MbCO but does not bind to deoxy Mb. OA binding to Mb, however, does not alter its O affinity. Without any Mb, muscle has a significantly lower level of triglyceride (TG). In Mb knock-out (MbKO) mice, both heart and skeletal muscles have lower level of TG relative to the control mice. Training further decreases the relative TG in the MbKO skeletal muscle. Nevertheless, the absence of Mb and lower TG level in muscle does not impair the MbKO mouse performance as evidenced by voluntary wheel running measurements. The results support the hypothesis of a complex physiological role for Mb, especially with respect to fatty acid metabolism.
最近的研究表明，肌红蛋白（Mb）除了储存和运输氧气外，可能还具有其他细胞功能。事实上，核磁共振实验表明，饱和脂肪酸（FA）棕榈酸酯（PA）可以在其结合状态（MbCO和MbCN）下与肌红蛋白（Mb）相互作用，但在其脱氧状态下不与Mb相互作用。这一观察结果引发了一个假说，即Mb也可以作为脂肪酸转运体。本研究使用更易溶解但不饱和的脂肪酸油酸（OA），进一步研究脂肪酸与Mb生理状态的相互作用。OA与MbCO结合，但不与脱氧Mb结合。然而，OA与Mb的结合并不改变其对氧气的亲和力。没有任何Mb时，肌肉中的甘油三酯（TG）水平显著较低。在肌红蛋白敲除（MbKO）小鼠中，心脏和骨骼肌中的TG水平相对于对照小鼠都较低。训练进一步降低了MbKO小鼠骨骼肌中的相对TG水平。然而，如自愿轮转运动测量所示，肌肉中Mb的缺失和较低的TG水平并未损害MbKO小鼠的表现。这些结果支持了Mb具有复杂生理作用的假说，尤其是在脂肪酸代谢方面。
