DIRECT OXIDATION OF GLUCOSE-6-PHOSPHATE, 6-PHOSPHOGLUCONATE AND PENTOSE-5-PHOSPHATES BY ENZYMES OF ANIMAL ORIGIN
DIRECT OXIDATION OF GLUCOSE-6-PHOSPHATE, 6-PHOSPHOGLUCONATE AND PENTOSE-5-PHOSPHATES BY ENZYMES OF ANIMAL ORIGIN
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DOI：
10.1042/bj0500081
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发表时间：
1951-01-01
影响因子：
4.1
通讯作者：
GLOCK, GE
中科院分区：
文献类型：
--
作者：
DICKENS, F;GLOCK, GE
在动物组织中证明了D-葡萄糖-6-磷酸、6-磷酸-D-葡萄糖酸盐和D-核糖-5-磷酸氧化的直接途径，并显示与先前描述的酵母非常相似。肝（马、大鼠和兔）、肾（大鼠和兔）、脑（大鼠和兔）和大鼠肝癌的提取物能有效地氧化己糖一磷酸和6-磷酸己糖酸。骨骼肌（大鼠和兔）和家禽的Rous肉瘤活性较弱。核糖-5-磷酸被肝脏和肾脏氧化，而骨骼肌的氧化活性较低。所有3种底物的氧化都是辅酶II特异性的，并且独立于糖酵解途径进行，因为无机磷酸盐不是必需的且浓度高。(0.01[图片]）的氟化物和碘乙酰胺不抑制。部分分离的系统从大鼠和马的肝脏的影响，通过分级硫酸铵沉淀。馏分C（60-70%饱和度）特异性氧化6-磷酸葡萄糖酸盐。级分B（50-60%饱和度）氧化葡萄糖-6-磷酸和果糖-6-磷酸，但不氧化果糖-1，6-二磷酸。级分B+C通常是D-核糖-5-磷酸氧化所必需的，其速度约为D-阿拉伯糖-5-磷酸和D-木糖-5-磷酸氧化的5倍。核糖-5-磷酸氧化至少需要2种肝脏因子。其中之一是辅酶II特异性脱氢酶，另一种可能是一种醛缩酶。核糖-5-磷酸的脱氢在20[度]时非常缓慢，但在37[度]时快速，因此不同于葡萄糖-6-磷酸葡萄糖酸在20[度]时的快速脱氢。氰化物（0.01 [image]）不会抑制这些底物的氧化，可能会加速氧化的早期阶段。底物浓度。最大产量的50%初始速度接近。7.5 x 10-5[图像]对于单磷酸己糖和1.5 x 10-5[图像]对于6-磷酸葡萄糖酸脱氢酶。提出了由D-葡萄糖-6-磷酸氧化形成D-核糖-5-磷酸的机理。
A direct pathway for the oxidation of D-glucose-6-phosphate, 6-phospho-D-gluconate and D-ribose-5-phosphate was demonstrated in animal tissues and shown to resemble closely that previously described for yeast. Hexose monophosphate and 6-phosphoglucon-ate are actively oxidized by extracts of liver (horse, rat and rabbit), kidney (rat and rabbit), brain (rat and rabbit) and rat liver carcinoma. Skeletal muscle (rat and rabbit) and Rous sarcoma of the fowl are weakly active. Ribose-5-phosphate was oxidized by liver and kidney, and less actively by skeletal muscle. Oxidation of all 3 substrates is coenzyme II-specific and proceeds independently of the glycolytic route, since inorganic phosphate is not essential and high concns. (0.01 [image]) of fluoride and iodoacetamide do not inhibit. Partial separation of the systems from rat and horse liver was effected by fractional ammonium sulfate precipitation. Fraction C (60-70% saturation) oxidizes 6-phosphogluconate specifically. Fraction B (50-60% saturation) oxidizes glucose-6-phosphate and fructose 6-phosphate, but not fructose-1,6-diphosphate. Fractions B+C are generally necessary for D-ribose-5-phosphate oxidation, which is about 5 times as rapid as the oxidation of D-arabinose-5-phosphate and D-xylose-5-phosphate. At least 2 liver factors are necessary for ribose-5-phosphate oxidation. One of these is a coenzyme II-specific dehydrogenase and the other possibly a type of aldolase. The dehydrogenation of ribose-5-phosphate is very slow at 20[degree], but rapid at 37[degree], and thus differs from the rapid dehydrogenation of glucose-6-phosphogluconate at 20[degree]. Cyanide (0.01 [image]) does not inhibit the oxidation of these substrates and may accelerate the early stages of oxidation. The substrate concns. producing 50% of the max. initial velocities are approx. 7.5 x 10-5[image] for hexose monophosphate and 1.5 x 10-5[image] for 6-phosphogluconate dehydrogenases. A mechanism is suggested for the oxidative formation of D-ribose-5-phosphate from D-glucose-6-phosphate.