Protein Constituents of Spermatozoa 



89 



middle-pieces contained a high proportion of iron in the form of 

 haematin, as can be seen from Table 13. Iron as well as copper and 

 zinc, present in the tail and middle-piece of ram spermatozoon, is 

 largely non-dialysable. Iron occurs mainly as haematin some of 

 which appears to be free and the rest protein-bound, mostly in the 

 form of cytochrome. Copper belongs to a protein complex which 

 readily gives up the metal on treatment with acid, thus resembling 

 haemocuprein, the copper-protein isolated some time ago from 

 blood cells (Mann and Keilin, 1938). Zinc also forms a complex with 

 a protein but unlike the zinc-protein of blood cells it has negligible 

 carbonic anhydrase activity. 



Table 13. Content of total iron, haematin, zinc, and copper ^ in 

 mechanically disintegrated middle-pieces and tails of ram spermatozoa 



(Spermatozoa separated from seminal plasma by centrifugation and 

 washing; mechanically disrupted in Mickle's disintegrator; sperm-heads 

 removed by centrifugation. The supernatant fluid ('homogenate') which 

 represents disintegrated middle-pieces and tails was analysed before and 

 after dialysis. Its dry weight, expressed as mg./lOO ml. semen, was 3300 

 before, and 2960 after, dialysis.) 



Human semen, in contrast to ram, has a much higher zinc 

 content. The first to take notice of this were Bertrand and Vladesco 

 (1921) who found 5-3-220 mg. Zn/100 ml. semen. More recently, 

 the problem of seminal zinc was taken up by Mawson and Fischer 

 (1953) who found that apart from the high zinc content of human 

 seminal plasma which is derived from the prostatic secretion (see 

 p. 19), centrifuged spermatozoa of man also carry a considerable 

 zinc reserve of their own, nearly 2 mg./g. dry matter. Of this, how- 

 ever, only a minute fraction is endowed with carbonic anhydrase 

 activity. 



