158 The Biochemistry of Semen 



nucleotide) which as Winberg (1941) showed, is a characteristic 

 intracellular constituent of spermatozoa. The cozymase-catalysed 

 phase of fructolysis consists of two closely interwoven oxidoreduc- 

 tion processes (Mann, 19456; Mann and Lutwak-Mann, 1947). 



H3PO4 ATP 



_,, , ^ . (, Phosphotriose dehydrogenase ) t^, i , • • j 



Phosphotriose — ^^ . ^-^ Phosphoglyceric acid 



Y 



H2 NaF inhibits 



\ Y 



Cozymase Phosphopyruvic acid 



\ 



Ha cozymase 



i 



Lactic acid^ ; Pyruvic acid 



Lactic dehydrogenase -^ 



The first oxidoreduction involves the oxidation of phosphotriose 

 to phosphoglyceric acid by phosphotriose dehydrogenase, and a 

 simultaneous reduction of cozymase to dihydrocozymase; the oxida- 

 tion of phosphotriose is coupled with an esterification of inorganic 

 phosphate and the synthesis of ATP; the oxidation product, phos- 

 phoglyceric acid, is converted by enolase to phosphopyruvic acid, 

 the phosphate of which is transferred to ADP, thus producing 

 pyruvic acid and ATP. The second oxidoreduction is between 

 dihydrocozymase and pyruvic acid: dihydrocozymase is oxidized to 

 cozymase, and pyruvic acid is reduced by lactic dehydrogenase to 

 L(+)-lactic acid. When washed ram spermatozoa are treated with 

 fluoride (to inhibit enolase), and incubated with added phospho- 

 triose and pyruvate, the two oxidoreduction processes continue as 

 usual but in addition to lactic acid there is an accumulation of 

 phosphoglyceric acid. lodoacetate, on the other hand, abolishes the 

 oxidoreductions in washed sperm and thus deprives them of the 

 ability to produce lactic acid. 



The not unimpressive array of facts available from the outlined 

 studies on spermatozoa strengthens the belief that ATP is the car- 

 dinal link between the activity of spermatozoa on the one hand, 

 and carbohydrate metabolism on the other. In whole semen, ATP 

 acts continually as phosphate-donor and acceptor in the course of 

 fructolysis. The content of ATP and with it the motility of ejaculated 



