238 
Studies  on  Pepsin. 
Am.  Jour.  Pharm. 
April,  1919. 
tryptophane  (Adamkiewicz  Hopkins-Cole  reagent),  glycoprotein  and 
glycoproteose  (Molisch  reagent).  Tests  were  also  made  on  the 
filtrate  from  coagulable  protein,  for  proteoses  (by  addition  of  satu- 
rated zinc  sulphate,  ammonium  sulphate,  picric  acid  solutions),  and 
protoproteoses  (by  saturated  sodium  chloride  solution,  potassium 
ferrocyanide  in  acetic  acid  solution). 
Results. — Altogether,  nine  purified  products  were  prepared.  In- 
cluding the  basic  pepsin  material,  the  various  proteolytic  strengths 
of  the  enzyme  which  were  examined  ranged  from  1 : 2,000  to  1  '.40,- 
000  (U.  S.  P.  IX).    The  results  given  in  the  accompanying  Tables 
1  and  II,  are,  in  every  case,  based  on  duplicate  determinations  and, 
because  of  possible  variation  in  the  U.  S.  P.  pepsin  assay,  these 
estimations  were  carried  out  in  triplicate  by  two  different  observers. 
As  may  be  noted  from  Table  I,  the  purification  of  pepsin  is  ac- 
companied by  a  general  decrease  in  the  total  mineral  matter.  This 
ranges  from  an  ash  content  of  nearly  5.5  per  cent.,  in  the  case  of 
the  basic  ( 1  : 2,000)  product  down  to  about  2  per  cent,  with  the 
highest  proteolytic  strengths  obtained.  The  phosphoric  acid  con- 
tent, also,  shows  a  gradual  decrease  so  that  the  value  at  1  : 40,000  is 
less  than  one  third  that  of  the  basic  material.  Both  the  calcium 
oxide  and  total  sulphur  values  fluctuate  in  the  different  strengths,  but 
both  show  an  increase  in  the  purified  as  compared  with  the  un- 
purified  samples.  It  is  a  significant  fact  that  the  chlorides,  which 
are  present  to  the  extent  of  i.ig  per  cent,  (as  NaCl)  in  the  1 : 2,000 
sample,  practically  disappear  as  a  result  of  purification. 
Probably  the  most  important  data  are  furnished  by  the  various 
nitrogen  factors,  particularly  the  nitrogen  in  amino  acid  condition. 
Confirming  more  elaborately  the  results  found  by  Aldrich,18  there  is 
found  to  be  almost  a  uniform  decrease  in  a-amino  acid  nitrogen  so 
that  in  the  sample  testing  1  : 40,000  only  0.61  per  cent,  is  found. 
Corroborating  these  results,  it  will  be  noted  from  the  table  that  there 
are  steady  increases  in  both  the  coagulable  protein  nitrogen  and  that 
existing  as  proteoses,  while  the  peptone  nitrogen  like  that  of  the 
amino  acids  shows  a  decrease.  The  values  for  total  nitrogen  showed 
decided  variations  among  the  different  samples  with  no  significant 
change  as  the  purification  increases. 
All  of  the  different  strengths  of  the  pepsin  examined  show 
levorotation  in  very  nearly  the  same  degree,  so  that  this  factor  is 
apparently  unaltered  as  a  result  of  purification.    With  the  exception 
18  Aldrich,  /.  Biol.  Chem.,  vol.  23,  339,  1915. 
