214 



BIOCHEMISTRY OF BACTERIAL LUMINESCENCE 



DPNH2 were invariably necessary for luminescence (see Fig. 3). All 

 these studies suggested that the luminescent system is a DPN-coupled 

 respiratory pathway, while the two- to threefold increase obtainable 

 with FMN in the presence of excess DPNH2 suggested that the oxi- 

 dase was coupled to oxygen via flavin. That such is indeed the case 

 was clearly demonstrated by the work of McElroy, Hastings, and 



CONCN OF DPNHj (moles « 10" ) 



Fig. 3. Effect of DPNHo concentration on bacterial extract luminescence: 36 fig 

 of palmitic aldehyde plus 4 /j.g of FMN were added to 0.3 ml of an aqueous 

 extract of acetonized powders (4.0 g/100 ml) dissolved in 0.1 M phosphate 

 buffer (pH 7.0); total volume, 3.0 ml. DPNH2 added as indicated. 



