Protein Constituents and Enzymes of Seminal Plasma 113 



for human seminal plasma, is probably due to this mucoid sub- 

 stance (Wislocki, 1950). 



The proteoses in trichloroacetic acid extracts from semen, which 

 one encounters not only in man, but also in the ram, bull, boar, 

 and other species, occasionally interfere with chemical analyses of 

 certain non-protein constituents. To overcome this difficulty, it is 

 advisable to replace trichloroacetic acid with other deproteinizing 

 agents such as zinc hydroxide, tungstic acid, phosphotungstic acid 

 or ethanol. Another source of trouble encountered in analytical 

 work with semen and due to the mucinous substance in seminal 

 plasma, human in particular, is that on centrifugation the mucus 

 has a tendency to form a stringy mass which firmly adheres to the 

 sperm cells. Caution must therefore be exercised in attributing to 

 spermatozoa as such, analytical results obtained with centrifuged 

 human semen. 



Several assays of free amino acids in mammalian seminal plasma 

 have been carried out, mostly however, by chromatographic or 

 microbiological methods, and not by chemical isolation. A notable 

 exception is the work of Wagner- Jauregg (1941) who isolated 

 crystalline tyrosine from an ethanolic extract of human semen. The 

 following free amino acids were found to occur in the seminal plasma 

 of man, glycine, threonine, alanine, valine, leucine, isoleucine, 

 cystine, proline, tyrosine, phenylalanine, lysine, arginine, aspartic 

 acid and glutamic acid (Jacobsson, 1950; Lundquist, 1952). In 

 bovine seminal plasma serine, glycine, alanine, aspartic acid and 

 glutamic acid were found (Gassner and Hopwood, 1952), and a 

 similar pattern was also observed in the seminal vesicle secretion 

 and in the ampullar fluid, the latter containing in addition a trace of 

 tyrosine. According to Gassner, the free amino acids in bull seminal 

 plasma disappear after castration, like seminal fructose and citric 

 acid, but their content is not restored by testosterone administra- 

 tion; furthermore, vasectomy alone, which is without effect on the 

 content of fructose, causes a disappearance of amino acids from bull 

 seminal plasma. 



Free amino acids occur also in fish semen; as long ago as 1923, 

 leucine, lysine and alanine have been isolated in pure form from 

 protein-free extracts of herring testicles (Steudel and Suzuki, 1923). 



There are indications that the amino acids and proteoses present 



