DAI H) n. KROGMANN ()l!> 



H2O2 Generation and Measurement 



^ d amino acid . , u r>, _i_ m u 



d alanine + Oo -, ^pyruvate + H2O2+ N H3 



oxidase 



, catalase x ,j u j _i_u n 



HoOo + elhanol >acetaldehyde + H2O 



alcohol ,, , , r^r-iM 



acetaldehyde + DPNH— — ^ ethanol+DPN 



' dehydrogenase 



pyruvate+DPNH ^^^ > lactate + DPN 



dehydrogenase 



Fig. 3. Reaction sequence for the generation and measurement of 



hydrogen peroxide. 



The next experiment (Table 3) shows the results of a Mehler re- 

 action assay and the lack of effect of indophenol dye on the reduction 

 of oxygen to hydrogen peroxide by illuminated chloroplasts. The 

 generation of hydrogen peroxide is the same in the presence or 

 absence of dye, in contrast to the dramatic stimulation of oxygen 

 exchange caused by indophenol in the mass spectrometer measure- 

 ments. It is also apparent that there is no obvious stoichiometric re- 

 lationship between the amount of hydrogen peroxide produced and 

 the phosphate esterified. 



The dye-stimulated oxygen exchange by illuminated chloroplasts 

 does not appear to result in hydrogen peroxide formation as might 

 be expected from Mehler's experiments. The rate of thirty to fifty 

 microatoms of oxygen consumed and evolved per milligram of chloro- 

 phyll per hour in the presence of indophenol dye is to be contrasted 

 to a rate of six to ten micromoles of hydrogen peroxide produced per 

 milligram of chlorophyll per hour regardless of the presence of 

 indophenol dye. 



The final diagram (Fig. 4) represents, in minimum detail, our 

 very tentative interpretation of the facts at hand. The dye is reduced 

 by the Hill reaction and Go is evolved as usual, but in such fashion 



