为什么乳酸菌及其发酵食品往往有利于健康?或许这正是由于其产乳酸盐的作用。乳酸盐代谢已经得到了生理和生物化学家的广泛关注。然而,20世纪的前叶,乳酸盐还一直被作为废物,特别是作为肌肉疲劳的罪魁祸首。但是最近,越来越多的研究结果证明,乳酸盐在多细胞有机体中发挥了关键性作用。已经证明乳酸有多种生理功能,可以作用于机体的激素释放、调节多种酶活性,控制机体代谢平衡。此外,这些特性还直接关系到病理作用的发生和发展,如糖尿病和癌症。乳酸盐不能简单地认为是一种厌氧发酵产物,其实更应该把它作为一个调节分子,可以调节和整合多条代谢途径。虽然乳酸盐本身并不是一种具氧化还原作用的化合物,但是,它作为一种重要的中间代谢产物参与了糖酵解、生物氧化和生物合成。乳酸盐在胞浆中由糖酵解途径合成,通过和丙酮酸之间的互相转化与NADH/NAD+偶联,由乳酸脱氢酶催化。所以乳酸盐在NADH/NAD+、pH值、ATP、生物氧化与合成的动态平衡中发挥着重要作用。也正是因为这些生物活性,乳酸盐已经被广泛应用于发酵和功能性食品生产、肉类食品质量保护和护色、防癌、抗癌;同时,乳酸盐还是生理变化、应激和病理评估的理想标志物。
The reason why lactic acid bacteria and its fermented food are helpful for health in most situations may be due to the production of lactate.The metabolic role of lactate has gained extensive attentions from physiologists and biochemists.However,during the first half of the last century,lactate has been designated as a waste product,especially for the controversial role in muscle fatigue.Currently,more and more publications are exploring and unveiling the critical roles of lactate in multicellular organisms.Lactate has been described as modulation enzymes with catalytic properties to affect hormonal release and responsiveness,and control body homeostasis.Moreover,these properties are directly related to the genesis and sustainability of pathological conditions such as diabetes and cancer.Lactate should not be regarded simply as an anaerobic metabolite,but should be considered as a regulatory molecule that modulates the integration of metabolism.Although lactate is not a redox product,it is an important intermediate metabolite for glycolysis,biological oxidation and biosynthesis.Lactate is produced in the cytosol by the fermentative branch of glycolytic pathway through the reduction of pyruvate with the concomitant oxidation of NADH to NAD+,a reaction catalyzed by lactate dehydrogenase(LDH).Therefore,lactate plays key roles in maintaining the dynamic equilibrium of NADH/NAD+,pH,ATP and biological oxidation/biosynthesis.Due to its multiple bioactivities,lactate is widely used in fermented and functional food,meat quality and color protection,and cancer prevention and resistance so that it is an ideal marker for evaluating physiological alteration,stress and pathology.