乳酸代谢通量调控规律的研究

选取了8株嗜酸乳杆菌进行分批发酵培养，分别测定了它们对数生长期乳酸发酵途径中10种相关酶的活性，分析了乳酸的代谢通量，并首次引入数量遗传学方法利用通径分析研究了酶活性对乳酸通量的直接和间接影响，建立了类似于代谢控制系数的决定系数R2(i)。该系数实际上反映了酶对乳酸通量的控制程度，研究结果显示，丙酮酸激酶(R2(PK)=0.3705)、己糖激酶(R2(HK)=0.3053)、磷酸丙糖异构酶(R2(TPI)=0.2733)和乳酸脱氢酶(R2(LDH)=0.2601)对乳酸通量具有相对较高的决定系数，对乳酸通量起主要控制作用；3-磷酸甘油醛脱氢酶(R2(GAPDH)= -0.1320)的决定系数为负值，对乳酸通量具有较为明显的负控制作用。本文首次应用数量遗传学方法研究相关酶对乳酸代谢通量的控制作用，这将为代谢控制分析提供新的思路。

Metabolic Flux Regulation for Lactic Acid Production

Eight Lactobacillus acidophilus strains were cultivated in batch, and the activities of 10 enzymes involved in lactic acid fermentation pathway were measured, and the metabolic fluxes of lactic acid were analyzed at the logarithmic growth phase. Path analysis was used to investigate the direct and indirect influence of enzyme activity on lactic acid metabolic flux, followed by the establishment of a determination coefficient (R2(i)) which quantified the control effect similar to metabolic control coefficient. Results showed that pyruvate kinase(R2(PK) = 0.3705), hexokinase(R2(HK) = 0.3053), triosephosphate isomerase(R2(TPI) = 0.2733) and lactate dehydrogenase (R2(LDH) = 0.2601) exhibited higher determination coefficients, which suggested that they played a dominant role in control of lactic acid production. However, the determination coefficient of gylceraldehyde-3-phosphate dehydrogenase was negative (R2(GAPDH) = 0.1320), which suggested that GAPDH had a negative effect on lactic acid production.