VOL. 12 (1953) 



PATHWAYS OF ACETATE OXIDATION 



243 



increasing the acidity of the solution, increasing the concentration of malonate, or 

 decreasing the number of cells. In yeast cells at pH 4.0 with phthalate buffer, it was 

 found that the effect of malonate depended on the amount of yeast used per vessel. 

 With 51 mg of yeast, there was practically no inhibition (7.5% inhibition). When the 

 amount of yeast was reduced to 5.1 mg malonate inhibited the oxidation of acetate by 



TABLE III 



OXIDATION OF INTERMEDIATES OF THE CITRIC ACID CYCLE 



BY Tetrahymena geleii 



Phosphate buffer, 0.03A/, pH 5.54. Substrates, o.oiM except pyruvate, o.oo5JV/. Malonate, 



0.02M. Temp. 26°. Time, 180 min. 



TABLE IV 



OXIDATION OF ACETATE, iSOCITRATE, AND SUCCINATE BY MICRO-ORGANISMS. 

 SYNTHESIS OF CITRIC ACID BY THEIR CELL-FREE EXTRACTS. 



Oxidation: Buffer, K-phosphate, 0.03M, pH 5.53; substrate, o.oiM; temp. 38°. 

 Citrate Synthesis: cell-free extract, iml; K-phosphate buffer, pH 7.4, 25 fxM; MgClj, ^[iM; 

 Cysteine, lo/nM; K oxalacetate, 20/uM; Acetyphosphate, 10/iiM; Coenzyme A, 50 units. Temp. 26°. 

 Time of incubation, 2 hours. Figures refer to /j,M citric acid formed per mg protein. 



Micro-organism 



O2 Uptake, blank substr acted 

 Acetate Isocitrate Succinate 



Citrate Synthesis 



liM 



TABLE V 



OXIDATION OF JSOCITR.'VTE BY CELL-FREE EXTRACTS OF MICRO-ORGANISMS 

 WHICH DO NOT OXIDIZE ADDED ISOCITRATE 



System: cell-free extract, i ml; K phosphate buffer, pH 7.56, o.i M, 0.5 ml; MgClg, 0.2M, 

 0.1 ml; K isocitrate, 2.16 fiM, 0.2 ml; HgO, i.i ml.TPN, 0.16 [xM, o.i ml added at time o. Temp. 36°. 



Micro-organism 



References p. 24g. 



Protein 



Reduction of 

 o.oys ^lM TPN 



Reduction rate calc. 

 per mg protein 



mgs 



seconds 



seconds 



