VOL. 12 (1953) AMINO ACID INTERACTIONS IN STRICT ANAEROBES 



113 



Table X) . Approximately equimolar increases in oxygen uptake and ammonia formation 

 take place (Expt. 4. Table X). 



TABLE X 



EFFECTS OF PYRUVATE AND Q-KETOGLUTARATE ON OXYGEN UPTAKE OF RESTING 



CI. sporogenes in presence of alanine 

 Warburg manometer vessels contained i ml suspension (in 0.15 M KCl) freshly prepared 

 CI. sporogenes in 0.02 M phosphate buffer pH 7.3. DL-alanine = 0.04 M. Pyruvate = 0.01 M. a-Keto- 

 glutarate = o.oi M. Gas = air. Temp. 37°. 



These results become immediately understandable on the following grounds: (a) 

 hydrogen peroxide is formed during the aerobic oxidation of L-alanine (b) hydrogen 

 peroxide is highly toxic to the amino acid oxidase (c) hydrogen peroxide is destroyed 

 (non-enzymically) by pyruvate. 



On this hypothesis, hydrogen peroxide is formed during the aerobic oxidation of 

 the amino acid, much of it being destroyed by pyruvate which is formed simultaneously. 

 Eventually, however, sufficient hydrogen peroxide accumulates to exert highly toxic 

 effects, the corresponding quantity of undecomposed pyruvic acid being insufficient in 

 quantity to be detected by ordinary chemical tests. The addition of pyruvate (or 

 a-ketoglutarate) to the system, however, prevents the accumulation of hydrogen peroxide 

 and the initial velocity of alanine oxidation proceeds unchecked, the pyruvate and 

 hydrogen peroxide that are simultaneously formed interacting with each other. Thus the 

 added pyruvate (or a-ketoglutarate) will not disappear (within experimental accuracy), 

 whereas the rate of alanine oxidation will be increased. 



It follows, from this view, that if oxygen is substituted for air, the rate of alanine 

 oxidation by resting CI. sporogenes will be diminished, as it is to be expected that the rate 

 of hydrogen peroxide formation during the oxidation of the amino acid, by presumably 

 the flavoprotein system, will be greater in oxygen than in air (see Mann and Quastel^^). 

 The results of experiment (shown in Table X) verify this prediction. In the presence of 

 oxygen, both the rates of oxygen uptake and of ammonia liberation by DL-alanine in 

 presence of CI. sporogenes are markedly retarded, and the stimulating effect of added 

 pyruvate is decreased. 



References p. 120. 



