Am.  Jour.  Pharm.  ) 
April,  1921.  J 
Studies  on  Pepsin. 
255 
obtained  a  nucleo  proteid  and  was  able,  under  certain  conditions, 
to  separate  an  albumose. 
Nencki  and  Sieber,  using  as  initial  material  juice  obtained 
through  gastric  fistula  in  dogs,  claim  to  have  secured  an  active  pepsin 
preparation  through  precipitation  which  is  free  from  albumin.  At 
the  same  time,  they  consider  the  precipitate  of  transparent  granules 
containing  chlorine  which  they  obtained  by  strongly  cooling  the 
gastric  juice  to  be  a  chemical  individual,  and,  in  all  probability, 
the  true  enzyme.  They  also  submit  analyses  to  support  their  con- 
tentions. Pekelharing,  in  a  later  investigation,  in  which  he  em- 
ployed the  artificial  juices  extracted  from  several  hundred  hog' 
stomachs  by  his  previous  method,  and  also  the  juice  obtained  from 
gastric  fistula  in  dogs,  disproved  this  view.  He  found  pepsin  to 
be  free  from  phosphorus  and  to  contain  no  nucleo  proteid,  but  the 
analyses  of  his  preparations  showed  no  constancy  in  results. 
That  a  protein-free  pepsin  solution  having  digestive  action  is 
possible,  has  also  been  maintained  by  Schrumpf.  The  latter  pre- 
pared a  Buchner-pressed  extract  of  hog  stomachs,  clarified  by 
filtration,  and  dialyzed  against  running  water.  The  dialysate  thus 
obtained  was  precipitated  by  addition  of  cholesterin  in  alcohol-ether 
solution,  filtered,  the  precipitate  redissolved  in  water,  and  the  sus- 
pension finally  clarified  by  a  Kitasato  candle.  The  clear  filtrate, 
while  giving  none  of  the  protein  reactions,  still  showed  powerful 
digestive  activity. 
The  amino  acid  constituents  of  pepsin  have  been  investigated 
by  Hugounenq  and  Morel  using  an  autodigested,  hydrochloric  ex- 
tract of  hog  stomachs.  They  conclude  that  an  extract  of  pepsin 
contains  a  number  of  monoamino  acids  in  the  free  state,  probably 
formed  in  the  autodigestion.  Glycocoll,  asparitic  and  glutaminic 
acids,  and  also  histidin,  they  found  to  be  absent  in  the  material 
examined. 
It  is  thus  readily  apparent  that,  as  true  with  other  enzymes, 
the  chemical  nature  of  pepsin  is  still  an  open  question.  Nearly  all 
of  the  above  investigators  have  based  their  conclusions  on  crude 
preparations,  undoubtedly  containing  admixed  or  combined  im- 
purities. Seemingly,  no  attempt  has  been  made  to  prove,  by  quan- 
titative measurements  of  the  proteolytic  activity,  that  an  actual 
purification  has  taken  place,  where  such  is  mentioned.  The  present 
investigation  was  undertaken  by  us  to  determine  what  changes 
take  place  in  the  purification  of  pepsin,  with  the  view  of  possibly 
throwing  some  light  on  the  chemical  nature  of  the  enzyme. 
