204 BACTERIOT.OOTCAL CITEMTRTRV 



carbon dioxide (sec p. 249) similarly takes place with 

 CO -enzyme I acting as hydrogen acceptor, and then 

 becoming re-oxidised. 



Co -enzyme I plays a similar role in the action of alde- 

 hyde mutase in producing alcohol and acetic acid from 

 acetaldehyde : — 



+ H2O 



(1) CH3CHO + Co-enzynie I > CH3COOH + reduced co-enzyme I 



(2) Reduced co-enzyme I + CH3CHO > Co-enzyme I + C2H5OH. 



The overall effect is the coupled oxidation and 

 reduction of acetaldehyde : — 



2CH3CHO + HoO > CH3CH2OH + C'HgCOOH. 



The dismutation of triose phosphate in yeast fermenta- 

 tion takes place by the same mechanism (see page 276). 



Co -enzyme II, triphosphopyridine nucleotide, con- 

 stituted similarly to co -enzyme I but containing three 

 instead of two phosphate groups, behaves in the same 

 way in the conversion of hexose-monophosphate to 

 phosphohexonic acid, and in the citric acid cycle. 



The f la vo -protein enzymes which participate in the 

 oxidation of dihydroco -enzymes contain the prosthetic 

 group, riboflavin adenine di -nucleotide, which acts as 

 hydrogen acceptor from the dihydroco -enzyme and gives 

 rise to the colorless dihydro compound (see opposite page) ; 



