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【答案】应助回帖
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爱与雨下: 金币+1 2017-02-15 07:44:59
HHHe(fjtony163代发): 金币+30, 代发 2017-03-17 04:03:33
fjtony163: 翻译EPI+1, 代发 2017-03-17 04:03:45
Flow of matter from formaldehyde to archaic citric acid cycle
As shown in the Figure 1 (reaction a), the interaction of two molecules of formaldehyde leads to the
formation of glycolaldehyde (Breslow, 1959). It is believed that glycolaldehyde is autocatalytic to its own formation and in the formose cycle an additional molecule of glycolaldehyde is produced from two other molecules of formaldehyde (Breslow, 1959). Both dihydroxyacetone and glyceraldehyde are intermediates of the formose cycle. The formation of methylglyoxal from either glyceraldehyde or from dihydroxiacetone is possible (Figure 1. reaction e) (Fedoronko and Königstein, 1969). The reaction itself is an acid-base catalyzed dehydration (Fedoronko and Königstein, 1969).Thus, as an offshoot of the formose cycle methylglyoxal can be generated. The conversion of methylglyoxal into lactate is an intramolecular Cannizzaro reaction (Figure 1). Methylglyoxal is first hydrated and then attacked by a hydroxy group resulting in a giving down of one molecule of water (Figure 1, reactions f and g). The subsequent steps are not fully corroborated, but it seems that lactate is resulted from the reaction (Figure 1, reactions h and i) (Fedoronko and Königstein, 1969, 1971).A critical point is the conversion of lactate into pyruvate(Figure 1, reaction j).
从甲醛到经典柠檬酸循环的化合物流转示意图 图1所示（反应a），两分子甲醛相互作用形成乙醇醛（Breslow, 1959）。据信乙醇醛可以自身催化其形成，并且在甲醛聚糖循环中一个额外的乙醇醛分子产自两分子甲醛（Breslow, 1959）。二羟基丙酮和乙醇醛都是甲醛聚糖循环的中间体。从乙醇醛或者二羟基丙酮形成丙酮醛都是可能的（图1. 反应 e）（Fedoronko and Königstein, 1969）。反应本身是个酸碱催化脱水的反应(Fedoronko and Königstein, 1969)。因此，作为甲醛聚糖循环的分支能够产生丙酮醛。丙酮醛转变成乳酸是分子内Cannizzaro反应（图1）。丙酮醛先水合，然后被羟基进攻失去一分子水（图1, 反应f和g）。后续步骤未能完全证实，但是乳酸可能是来自对应反应（图1, 反应h和i）（Fedoronko and Königstein, 1969, 1971）。一个关键点是乳酸转变为丙酮酸（图1, 反应j）。 |
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