Protein Constituents and Enzymes of Seminal Plasma 1 1 7 



Amino acid oxidase 



In addition to sugars and fatty acids, spermatozoa are capable 

 of oxidizing a number of amines and amino acids. The oxidative 

 deamination of amino acids by bull spermatozoa has been the subject 

 of a study by Tosicand Walton (1945; 1946«, b, 1950). The starting 

 point of this study has been the observation that the addition of 

 egg-yolk to bull sperm causes an increased oxygen uptake, which, 

 however, gradually declines in about an hour's time. Egg-yolk 

 fractionation led to a dialysable, nitrogen-containing fraction which 

 was oxidized by spermatozoa. The oxidation was accompanied by 

 accumulation of ammonia and formation of hydrogen peroxide. 

 Evidence was obtained which pointed to peroxide being responsible 

 for the gradual decline in the oxygen uptake by spermatozoa. 



In the course of their study, Tosic and Walton examined several 

 pure amino acids and found that spermatozoa oxidize three natur- 

 ally occurring amino acids, namely L-tyrosine, L-phenylalanine and 

 L-tryptophan. According to Tosic (1947, 1951), the hydrogen- 

 peroxide-forming aerobic process in bull semen is an oxidative 

 deamination catalysed by the L-amino acid oxidase of spermatozoa, 

 which differs from the analogous enzyme of other animal tissues 

 by having its range of activity restricted to only three aromatic 

 amino acids; the activity of the enzyme can be expressed by the 

 equation 



R CH2CHCOOH+O2+H2O — > R CH, C COOH+H2O2+NH3 



I "II 



NH2 O 



Seminal phosphatases 



Semen owes its powerful phosphatase activity mainly to the 

 seminal plasma which carries several different dephosphorylating 

 enzymes derived from the male accessory organs of reproduction. 

 Among the most active and best known enzymes in this group are the 

 so-called 'acid phosphatase' and 'alkaline phosphatase'. In addition 

 to these two phosphomonoesterases, the seminal plasma contains 

 '5-nucleotidase', a pyrophosphatase, and several adenosinetri- 

 phosphatases. 



In early studies on phosphatases, the substrates commonly 



