Miki Kiyoshi
Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina 27599-7090, USA.
Soc Reprod Fertil Suppl. 2007;65:309-25.
Energy metabolism is a key factor supporting sperm function. Sustaining sperm motility and active protein modifications such as phosphorylation could be the reason why sperm require exceptionally more ATP than other cells. Many methods have been used to understand the relationship between energy metabolism and sperm function. These approaches have identified critical metabolic pathways that support specific processes during germ cell development and fertilisation. In round spermatids, lactate and pyruvate are the preferred substrates and the use of glucose is limited, however, during epididymal maturation sperm expand to use glycolysis. While the acrosome reaction requires lactate or pyruvate for ATP production by oxidative phosphorylation, gamete fusion requires glucose to produce NADPH by the pentose phosphate pathway. Sperm motility appears to be supported by relatively low ATP levels, but achievement of high ATP levels are essential for tyrosine phosphorylation linked to hyperactivation. Thus, each individual process and event requires a different substrate and metabolic pathway. Despite different preferences for energy substrates and metabolic pathways between species, analysis of knockout mice revealed that glycolysis is indispensable for mouse sperm function and that oxidative phosphorylation is not essential for male fertility. This suggests that glycolysis could compensate for the lack of oxidative phosphorylation and recover most sperm function. Spermatogenic cell-specific glycolytic enzymes may confer flexible use of substrates and adapt to unexpected conditions for substrates in the female reproductive tract.
能量代谢是支持精子功能的关键因素。维持精子活力以及诸如磷酸化等活跃的蛋白质修饰可能是精子比其他细胞需要格外多的ATP的原因。人们已使用多种方法来理解能量代谢与精子功能之间的关系。这些方法已确定了在生殖细胞发育和受精过程中支持特定过程的关键代谢途径。在圆形精子细胞中，乳酸和丙酮酸是首选底物，葡萄糖的利用有限，然而，在附睾成熟过程中，精子转而利用糖酵解。虽然顶体反应需要乳酸或丙酮酸通过氧化磷酸化产生ATP，但配子融合需要葡萄糖通过磷酸戊糖途径产生NADPH。精子活力似乎由相对较低的ATP水平支持，但达到高ATP水平对于与超活化相关的酪氨酸磷酸化至关重要。因此，每个单独的过程和事件都需要不同的底物和代谢途径。尽管不同物种对能量底物和代谢途径有不同偏好，但对基因敲除小鼠的分析表明，糖酵解对于小鼠精子功能是不可或缺的，而氧化磷酸化对雄性生育力并非必不可少。这表明糖酵解可以弥补氧化磷酸化的不足并恢复大多数精子功能。生精细胞特异性糖酵解酶可能赋予底物灵活利用能力，并适应雌性生殖道中底物的意外情况。
