Fructose and Fructolysis 135 



Thus, in the light of the evidence available until relatively recently, 

 it seemed rather improbable that in the normal, fully-developed 

 mammalian organism, fructose could occupy a place on the list 

 of 'animal carbohydrates', or that any specific function could be 

 assigned to this sugar. 



Fructose as a normal constituent of semen 



Since the early researches on mammalian semen by McCarthy, 

 Stepita, Johnston and Killian (1928), Ivanov (1931), Huggins and 

 Johnson (1933) and other pioneers in the field of semen biochemistry, 

 it was known that in several species, including man, a reducing and 

 yeast-fermentable sugar is normally present in semen, the concen- 

 tration of this sugar exceeding by far that of glucose in blood. 

 However, up to 1945, in the extensive literature dealing with the 

 subject of seminal sugar, this substance has been described either as 

 glucose or simply as the reducing sugar of semen (Killian, 1933; 

 Bernstein, 1933; Goldblatt, 1935«; Shergin, 1937; McKenzie, Miller 

 and Bauguess, 1938; Davis and Cole, 1939; Moore and Mayer, 

 1941; MacLeod and Hotchkiss, 1942; Salisbury and VanDemark, 

 1945), and the only reference to a probable occurrence of fructose 

 in semen is found in an early paper by Yamada (1933) who in a 

 general survey of human tissues and body fluids carried out numer- 

 ous fructose determinations by means of a colour reaction with the 

 drug 'cryogenine'; of course, like so many colour tests, this reaction 

 by itself cannot be regarded as specific for fructose, since it gives 

 a positive result not only with fructose but also with other ketoses, 

 nor does it distinguish between free fructose, that is D(-)-fructo- 

 pyranose (formula in Fig. 14), and bound fructose, i.e. fructofura- 

 nose, such as occurs for example, in the various phosphofructoses . 



In 1945, in the course of studies on the metabolism of semen, the 

 seminal sugar was isolated for the first time and identified by chemi- 

 cal methods as free D(-)-fructose (Mann, \9A5b\ \946a, b, c). The 

 actual final isolation was accomplished with a 120 ml. sample of bull 

 semen representing some thirty pooled bull ejaculates, which were 

 collected within a twelve-hour period by the various Centres for 

 Artificial Insemination of Cattle in England, and immediately des- 

 patched to Cambridge. The chemical procedure involved the fol- 

 lowing steps: (a) the preparation of methylphenyl-fructosazone, a 



