1 74 The Biochemistry of Semen 



semen, on the other hand, has been found by Sekine (1951) to be 

 highly active, the activity being more concentrated in the sperma- 

 tozoa than in the seminal plasma. According to this author, boar 

 spermatozoa, both epididymal and ejaculated, possessed choline 

 esterase activity as high as that of brain, whereas the seminal plasma 

 was only one-third as active as human blood serum. Boar sperma- 

 tozoa, although highly active against acetylcholine, were found at 

 the same time to be completely inactive against benzoylcholine 

 which suggests that their choline esterase is of the 'true' or 'specific' 

 type. Results obtained on ram semen (Legge and Mann, unpublished 

 data) lead to a similar conclusion; ram spermatozoa exhibited a high 

 activity at low concentrations of acetylcholine but were poorly 

 active at high substrate concentrations, and hydrolysed efficiently 

 acetyl-i9-methylcholine but were ineffective against benzoylcholine. 

 A study was also made at the same time of the distribution of the 

 enzyme between the sperm-heads and -tails, using ram spermatozoa 

 disintegrated with glass beads in the Mickle mechanical shaker (see 

 p. 87). Choline esterase occurred mainly in the tail fraction. 



ERGOTHIONEINE 



Ergothioneine was first discovered by Tanret (1909) who isolated 

 it from rye ergot. Two years later, Barger and Ewins (1911) identi- 

 fied the new substance as a betaine of thiolhistidine (^-2-thiolglyoxa- 

 line-4(5)-propiobetaine). The final confirmation of the structure was 

 provided by Heath, Lawson and Rimington (1950, 1951) who suc- 

 ceeded in synthesizing ergothioneine from 2-thiolhistidine; the latter 

 is an amino acid which so far has never been found in nature 

 but was prepared synthetically by Harington and his co-workers 

 (Ashley and Harington, 1930; Harington and Overhoff, 1933), and 

 shown by Neuberger and Webster (1946) to be unable to replace 

 histidine as a growth-promoting factor in animals. 



/-NH 

 / \CH 



HS— C 



C— CH,CHCOO 



N^ +i(CH3)3 



Ergothioneine 



