ANTIBODIES AGAINST RESPIRATORY ENZYMES 371 



(13) Glycerofhosfhate dehydrogenase reversibly oxidizes 1-a-glyc- 

 erophosphate to 3-phosphoglyceraldehyde. 



(14) d-3-Phosphoglyceraldehyde is reversibly phosphorylated, yield- 

 ing d-glyceraldehyde-l,3-dipliosphate, in the presence of inor- 

 ganic phosphate (Meyerhof, 1941). 



(15) Phosfhoglyceraldehyde dehydrogenase dehydrogenates 1,3- 

 diphosphoglyceraldehyde to 1,3-diphosphoglyceric acid. Cozy- 

 mase I (DPN) functions as hydrogen acceptor (DPN^ 

 DPNH2). This reaction is inhibited by iodoacetate. 



(16) 1,3-Diphosphoglyceric acid obtained in reaction (15) is enzy- 

 matically dephosphorylated to d-3-phosphogly eerie acid. ADP 

 serves as phosphate acceptor (ADP^ATP). 



(17) Phos'phoglyceromutase converts d-3-phosphoglyceric acid to 

 d-2-phosphoglyceric acid. 



(18) Enolase catalyzes the removal of one molecule of water from 

 d-2-phosphoglyceric acid, yielding (ewoO-phosphopyruvic 

 acid. The reaction is reversible. The enzyme requires Mg"^ + , 

 Mn++, or Zn^^ for activation, probably, forming an active 

 metal protein complex. Enolase is strongly inhibited by 

 fluorides. The inhibition occurs in the presence of phosphate; 

 a magnesium-fluorophosphate complex is formed which dis- 

 places the magnesium from the enzyme. A high concentration 

 of pyrophosphate also inhibits enolase even in the absence of 

 fluoride; here also, probably, a magnesium pyrophosphate 

 complex is formed. 



(19) Phosfho-enol-transphos'phorylase reversibly dephosphorylates 

 (ewoO-phospho-pyruvic acid to pyruvic acid. Mg"*"^ is re- 

 quired, K+ is essential (Lardy and Ziegler, 1945), AMP or 

 ADP serves as phosphate acceptor (AMP^ADP; ADP:?± 

 ATP). Calcium ion inhibits the reaction. 



(20) In the muscle, pyruvic acid is reversibly reduced to lactic acid. 

 Cozymase I-dehydrogenase catalyzes this reaction. DPNH2 

 produced in reaction (15) can readily serve as hydrogen 

 donator, producing lactic acid. 



(21 ) In yeast, pyruvate is decarboxylated by carboxylase (Thiamine- 

 diphosphate as coenzyme) to acetaldehyde. 



(22) Acetaldehyde formed in reaction (21) is reversibly reduced 

 to ethyl alcohol by means of alcohol dehydrogenase 



