. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. VOL. 12 (1953) PATHWAYS OF ACETATE OXIDATION 245 1800 1500 1200 ])ed when 40% of the added malonate was oxidized (Fig. 4). The value of this oxidation was an indication of complete oxidation (HOOCCHgCOOH + 2 Og -= 3 CO2 + 2H20).The induction time, which may last as long as two hours when the amount of bacteria is small, was thought to be due to a slow decarboxylation of malonate preceding the oxidation (HOOCCH2COOH - CO2 + CH3COOH). The
. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. VOL. 12 (1953) PATHWAYS OF ACETATE OXIDATION 245 1800 1500 1200 ])ed when 40% of the added malonate was oxidized (Fig. 4). The value of this oxidation was an indication of complete oxidation (HOOCCHgCOOH + 2 Og -= 3 CO2 + 2H20).The induction time, which may last as long as two hours when the amount of bacteria is small, was thought to be due to a slow decarboxylation of malonate preceding the oxidation (HOOCCH2COOH - CO2 + CH3COOH). There was, however, no COg production when the bacterial suspension was incubated in the presence of malonate with nitrogen as the gas phase. In spite of this oxidation, malonate inhibited effectively acetate oxidation (Fig. 5). Inhibition of acetate oxidation by malonate maybe considered as evidence that the oxidation proceeds through the dicarboxylic or the tricar- boxylic acid pathway. There would be no inhi- bition if the oxidation proceeded through another pathway which had no succinate as an inter- mediate oxidation product. Negative experi- ments, however may mean only lack of penetra- tion of malonate. Thus acetate oxidation by moulds was not inhibited by malonate, although there were found in the culture media all the intermediates of the citric acid cycle. Malonate inhibition experiments could be utilized as an indication of the presence of the dicarboxylic acid cycle by determination of citric and suc- cinic acids after oxidation of acetate in the pre- sence and in the absence of malonate. It is known that baker's yeast produces citric and suc- cinic acids on oxidation of acetic acid^^, and that the pathway of this oxidation, mainly the tricar- boxylic acid cycle, can also be the dicarboxylic acid cycle^^'^'. In agreement with these views, on oxidation of acetate by yeast at pH there were found 44 mm^ of citrate, and traces of succinate, whereas in the presence of m
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