PENTOSE PHOSPHATE PATHWAY OF GLUCOSE METABOLISM - ENZYME PROFILES AND TRANSIENT AND STEADY-STATE CONTENT OF INTERMEDIATES OF ALTERNATIVE PATHWAYS OF GLUCOSE METABOLISM IN KREBS ASCITES CELLS
PENTOSE PHOSPHATE PATHWAY OF GLUCOSE METABOLISM - ENZYME PROFILES AND TRANSIENT AND STEADY-STATE CONTENT OF INTERMEDIATES OF ALTERNATIVE PATHWAYS OF GLUCOSE METABOLISM IN KREBS ASCITES CELLS
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DOI：
10.1042/bj1151009
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发表时间：
1969-01-01
影响因子：
4.1
通讯作者：
MCLEAN, P
中科院分区：
文献类型：
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作者：
GUMAA, KA;MCLEAN, P
1.研究了Krebs腹水细胞中戊糖磷酸途径的调节反应。为了比较，同时研究了糖酵解途径。2.戊糖磷酸途径酶的活性较低，与糖酵解酶的活性相反。葡萄糖-6-磷酸脱氢酶对底物和辅因子的Km值约为正常组织中该酶报道上限的4倍。1，6-二磷酸果糖和NADPH竞争性抑制6-磷酸葡萄糖酸脱氢酶。3.约28%的己糖激酶活性在细胞的颗粒部分中。可溶性酶的抑制果糖1，6-二磷酸和核糖5-磷酸，但不被3-磷酸甘油酸。本文报道了部分纯化的可溶性酶在体外模拟ATP、葡萄糖6-磷酸和Pifoundin浓度的系统中的行为。4.在向细胞中加入葡萄糖后的瞬态期间代谢物积累的动力学表明葡萄糖磷酸化的两个阶段，初始快速阶段随后突然缓慢阶段延伸到稳态。5.在戊糖磷酸途径中间体中，6-磷酸葡萄糖酸、景天庚酮糖7-磷酸和果糖6-磷酸的积累超过葡萄糖6-磷酸的积累。4-磷酸赤藓糖2 min达到稳态浓度，而戊糖磷酸线性积累。6.计算了戊糖磷酸途径反应的质量作用比。转酮醇酶反应在30秒时处于平衡。然后逐渐从平衡向稳态比率移动。葡萄糖6-磷酸脱氢酶在所有时间都远离平衡。7. [14 C]葡萄糖碳通量的研究证实了在腹水细胞中存在有效的戊糖磷酸途径，在对照细胞中占总通量的1%，在用吩嗪硫酸甲酯处理的细胞中占10%。8.通过直接氧化途径形成的戊糖磷酸和估计从14 CO2产量代表总积累的戊糖磷酸的20%，其他80%是由戊糖磷酸途径的非氧化反应形成的。9.磷酸戊糖途径似乎作为两个独立的途径起作用，两者都朝向磷酸戊糖形成起作用。这两种途径的控制进行了讨论。
1. The pentose phosphate pathway in Krebs ascites cells was investigated for regulatory reactions. For comparison, the glycolytic pathway was studied simultaneously. 2. Activities of the pentose phosphate pathway enzymes were low in contrast with those of the enzymes of glycolysis. TheKmvalues of glucose 6-phosphate dehydrogenase for both substrate and cofactor were about four times the reported upper limit for the enzyme from normal tissues. Fructose 1,6-diphosphate and NADPH competitively inhibited 6-phosphogluconate dehydrogenase. 3. About 28% of the hexokinase activity was in the particulate fraction of the cells. The soluble enzyme was inhibited by fructose 1,6-diphosphate and ribose 5-phosphate, but not by 3-phosphoglycerate. The behaviour of the partially purified soluble enzymein vitroin a system simulating the concentrations of ATP, glucose 6-phosphate and Pifoundin vivois reported. 4. Kinetics of metabolite accumulation during the transient state after the addition of glucose to the cells indicated two phases of glucose phosphorylation, an initial rapid phase followed abruptly by a slow phase extending into the steady state. 5. Of the pentose phosphate pathway intermediates, accumulation of 6-phosphogluconate, sedoheptulose 7-phosphate and fructose 6-phosphate paralleled the accumulation of glucose 6-phosphate. Erythrose 4-phosphate reached the steady-state concentration by 2min., whereas the pentose phosphates accumulated linearly. 6. The mass-action ratios of the pentose phosphate pathway reactions were calculated. The transketolase reaction was at equilibrium by 30sec. and then progressively shifted away from equilibrium towards the steady-state ratio. The glucose 6-phosphate dehydrogenase was far from equilibrium at all times. 7. Investigation of the flux of [14C]glucose carbon confirmed the existence of an operative pentose phosphate pathway in ascites cells, contributing 1% of the total flux in control cells and 10% in cells treated with phenazine methosulphate. 8. The pentose phosphate formed by way of the direct oxidative route and estimated from the14CO2yields represented 20% of the total accumulated pentose phosphate, the other 80% being formed by the non-oxidative reactions of the pentose phosphate pathway. 9. The pentose phosphate pathway appears to function as two separate pathways, both operating towards pentose phosphate formation. Control of the two pathways is discussed.