1 54 The Biochemistry of Semen 



sperm in a 'bound form' but is released in an 'active form' after 

 ejaculation. Continuing their study, these workers observed that 

 heat-inactivated bull semen, or semen and testicular extracts heated 

 with sodium hydroxide, increased the rate of aerobic fermentation 

 of sugars by baker's yeast, without affecting markedly yeast respi- 

 ration or anaerobic fermentation. The yeast-stimulating factor was 

 extracted with carbon tetrachloride from alkaline hydrolysates of 

 hog testes and obtained in the form of yellow coloured crystals 

 which proved to be elementary sulphur (Ghosh and Lardy, 1952). 

 Yeast reduces sulphur to HgS which is probably the agent ultimately 

 responsible for the stimulation of the aerobic fermentation. The 

 identity of the yeast factor with sulphur was verified by reproducing 

 the stimulating effect on yeast with pure rhombic sulphur. Sulphur 

 as such, however, cannot be the sperm 'regulator' since it is without 

 influence on the Pasteur effect in epididymal spermatozoa. On the 

 other hand, a number of sulphydryl compounds such as cysteine, 

 reduced glutathione and hydrogen sulphide have been found to 

 stimulate the respiration and aerobic glycolysis of epididymal 

 sperm and the possibility remains, that the 'metabolic regulator' 

 is, in fact, a sulphydryl compound, liberated during ejaculation 

 from the spermatozoa, with a sulphydryl group in labile form, which 

 can be easily removed and oxidized to sulphur by alkaline hydrolysis. 

 The peculiar changes in the metabolic properties of spermatozoa 

 during cold-storage of the epididymis, are equally in need of eluci- 

 dation. A problem which also deserves further biochemical study 

 is the 'ripening' phenomenon which takes place in the spermatozoa 

 while they remain in the epididymis. Presumably, the metabolism 

 of sperm in the epididymis is related in some as yet unknown 

 manner to the structural changes associated with sperm maturation 

 processes, such as the migration of the 'kinoplasmic droplet'. 



Intermediary reactions in sperm fructo lysis and the role of phosphorus- 

 containing coenzymes 

 The ability of washed spermatozoa to convert into lactic acid 

 equally well added fructose, glucose and mannose is due in all 

 probability to the fact that the metabolic degradation of these 

 three sugars is initiated by the sam.e hexokinase-catalysed reaction 

 with adenosine triphosphate. 



