DORMANCY OF BACTERIAL ENDOSPORE 93 



Although the data are as yet incomplete, it is reasonably safe 

 to conclude that the initial binding site is identical to or very 

 similar to the L-alanine dehydrogenase. One difficulty remains 

 in invoking its operation in L-alanine deamination — the equi- 

 librium constant for the reaction (Kequiv. = 1.3 X lO"^^) is in 

 favor of amination^^. In vegetative cells this enzyme is probably 

 the route of alanine synthesis. L-alanine utilization in spores may 

 yet be possible if the end products of the reaction, pyruvate and 

 DPNH are rapidly utilized, thus driving the reaction to the 

 right. As we have previously mentioned, pyruvate is metabolized 

 by spores but the rate is low. The oxidation of DPNH by the 

 DPA-stimulated soluble DPNH oxidase seems more likely. 

 This was tested by measuring the rate of NH3 release from 

 L-alanine in dialyzed extracts of activated spores^^. The results 

 (Fig. 9) show that the rate of deamination is dramatically 

 stimulated by DPA. DPA has no effect on the purified enzyme, 

 and since the DPNH oxidase is present in these extracts, its role 

 is undoubtedly that of recycling DPNH to DPN and thus 

 keeping a low level of DPNH present in the extract. 



The release of DPA during activation, therefore, can acceler- 

 ate the production of pyruvate via its stimulation of the DPNH 

 oxidase and thereby produce more rapidly the products of 

 pyruvate oxidation required for overall germination. 



CONCLUSION 



Our knowledge of the biochemical nature of the dormant 

 state is as yet fragmentary. Some information has been presented 

 indicating the role of the enzymes present in dormant and 

 activated spores in converting the dormant state to the vegeta- 

 tive one. One may view with optimism the possibiHty of soon 

 understanding the trigger mechanism involved in breaking the 

 dormant state. 



References p. 94 



