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首页> 外文期刊>The FEBS journal >Temperature and phosphate effects on allosteric phenomena of phosphofructokinase from a hibernating ground squirrel (Spermophilus lateralis).
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Temperature and phosphate effects on allosteric phenomena of phosphofructokinase from a hibernating ground squirrel (Spermophilus lateralis).

机译：温度和磷酸盐对冬眠地松鼠（Spermophiluslateralis）磷酸果糖激酶的变构现象的影响。

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摘要

Temperature effects on the kinetic properties of phosphofructokinase (PFK) purified from skeletal muscle of the golden-mantled ground squirrel, Spermophilus lateralis, were examined at 37 degrees C and 5 degrees C, values characteristic of body temperatures in euthermia vs. hibernation. The enzyme showed reduced sensitivity to all activators at 5 degrees C, the Ka values for AMP, ADP, NH4+ and F2,6P2 were 3-11-fold higher at 5 degrees C than at 37 degrees C. Inhibition by citrate was not affected whereas phosphoenolpyruvate, ATP and urea became more potent inhibitors at low temperature. While typically considered an activator of PFK activity, inorganic phosphate performed as an inhibitor at 5 degrees C. Decreasing temperature alone causes the actions of inorganic phosphate to change from activation to inhibition. We found that Km values for ATP remained constant while Vmax dropped significantly upon the addition of phosphate. Phosphate inhibition at 5 degrees C was noncompetitive with respect to ATP and the Ki was 0.15+or-0.01 mM (n=4). The results indicate that PFK is less likely to be activated in cold torpid muscle; PFK is less sensitive to changing adenylate levels at the low temperatures characteristic of torpor, and PFK is clearly much less sensitive to biosynthetic signals. All of these characteristics of hibernator PFK would serve to reduce glycolytic rate and help to preserve carbohydrate reserves during torpor.
机译：在37°C和5°C下检查了温度对从金黄地松鼠松鼠骨骼肌的骨骼肌中纯化的磷酸果糖激酶（PFK）动力学特性的影响，这是人体温度在正常状态下相对于冬眠状态的特征值。该酶在5°C下对所有激活剂的敏感性降低，AMP，ADP，NH4 +和F2,6P2的Ka值在5°C时比在37°C时高3-11-倍。柠檬酸盐的抑制作用不受影响，而磷酸烯醇丙酮酸，ATP和尿素在低温下成为更有效的抑制剂。无机磷酸盐通常被认为是PFK活性的活化剂，但在5摄氏度时作为抑制剂起作用。仅降低温度会使无机磷酸盐的作用从活化变为抑制。我们发现，添加磷酸盐后，ATP的Km值保持恒定，而Vmax显着下降。相对于ATP，在5摄氏度下的磷酸盐抑制作用是非竞争性的，Ki为0.15+或-0.01 mM（n = 4）。结果表明，PFK不太可能在冷muscle性肌肉中被激活。 PFK在玉米秸秆的低温特性下对改变腺苷酸水平不敏感，而PFK对生物合成信号显然不那么敏感。冬眠者PFK的所有这些特征将有助于降低糖酵解速率，并有助于在玉米粥中保存碳水化合物的储备。

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