Müller R, Babel W
Acta Biol Med Ger. 1981;40(2):123-35.
Purified 3-hexulosephosphate synthase (HPS) from the facultative methylotrophic Bacterium MB 58 exhibits a burst-like progress curve. The transition appears in an abrupt manner at physiological substrate concentrations. The following phase of lower activity again shows linear progress in the observation period. Effects of substrates, temperature or dilution on the enzyme can be ruled out as causes of this transition. However, it is obvious that it takes place after the same amount of product has accumulated. That the reaction product causes this diminution in velocity can be demonstrated by varying the enzyme concentration or the possibility for accumulating product or the product concentration itself. The substrates of HPS counteract this product-induced transition in that an increased amount of the former makes necessary an increased amount of the latter to trigger the transition. The shape of the progress curve and experiments with different amounts of in situ-generated or synthesized product show that no simple product inhibition is involved. For the explanation of all phenomena observed three enzyme forms showing different affinities for substrates and product are postulated. These forms may be interconverted into each other by substrates and product of HPS in a specific manner.
从兼性甲基营养细菌MB 58中纯化得到的3-己酮糖磷酸合酶（HPS）呈现出一种类似爆发的进程曲线。在生理底物浓度下，这种转变以突然的方式出现。在观察期内，随后较低活性阶段再次呈现线性进程。底物、温度或稀释对酶的影响可被排除作为这种转变的原因。然而，很明显这种转变是在积累了相同量的产物之后发生的。通过改变酶浓度、积累产物的可能性或产物浓度本身，可以证明反应产物会导致这种速度降低。HPS的底物会抵消这种产物诱导的转变，因为前者数量增加时，需要增加后者的量才能引发转变。进程曲线的形状以及使用不同量原位生成或合成产物的实验表明，其中不涉及简单的产物抑制。为了解释所观察到的所有现象，推测存在三种对底物和产物具有不同亲和力的酶形式。这些形式可能会被HPS的底物和产物以特定方式相互转化。
