376 
Action  of  the  Enzymes. 
f  Am.  Jour.  Pharm. 
(     August,  1911. 
when  accompanied  by  two  conditions — the  presence  of  water  and 
heat.  Nature's  economy  provides  that  it  shah  be  physiologically 
active  at  and  about  ioo°  while  an  exposure  of  its  simple  solution 
to  a  temperature  of  130°  F.  will  quickly  destroy  its  proteolytic  activ- 
ity. Moreover,  its  digestive  activity  is  always  dependent  on  the 
medium  in  which  it  is  exhibited.  The  U.S. P.  requires  that  one  grain 
of  pepsin  shall  be  able  to  digest  3000  grs.  of  coagulated  egg  albumin 
when  suspended  in  a  0.2  per  cent.  HCl  solution  with  water.  By 
repurification  this  standard  may  be  increased  to  a  much  higher 
potency ;  but  even  in  the  highest  degree  of  purification  that  it  has 
yet  been  obtained,  it  is  at  least  in  combination  with  nucleo-proteid 
bodies.  These  nucleo-proteids  are  combinations  of  nucleic  acid  with 
albumin.  Recently  several  authorities  have  advanced  the  theory 
that  the  nucleo-proteids  themselves  are  the  enzymes.  This  is  espe- 
cially urged  by  Haliburton,  and  Pekelharing  has  practically  arrived 
at  the  same  conclusion  and  suggests  that  the  nucleo-proteid  is  proba- 
bly the  zymogen  of  the  enzyme.  This  hypothesis  is  strengthened 
by  the  observations  of  McCallum,  who  showed  that  in  nature  the 
nucleus  initiates  the  process  of  secretion  and  excretes  some  material 
into  the  cytoplasm  which  then  undergoes  further  changes  and  ulti- 
mately enters  into  the  zymogen,  if  indeed  it  does  not  actually 
form  the  principal  part  of  it.  Nencki  and  Sieber  also  state  that 
pepsin  contains  nucleo-proteid  and  conclude  that  the  zymogen — 
pepsinogen — is  converted  into  pepsin  by  combining  with  the  nucleo- 
proteid  of  the  cell.  The  practical  results  of  pepsin  digestion  of 
nucleo-proteids  have  been  frequently  demonstrated.  Although  they 
are  much  more  resistant  to  hydrolysis  than  the  true  albumins, 
nevertheless  under  a  prolonged  peptic  digestion,  the  nucleo- 
proteids  are  split  into  nucleins,  being  new  compounds  of  nucleinic 
acid  and  protein  fractions. 
A  series  of  experiments  in  which  pepsin  and  its  natural  asso- 
ciates were  the  only  possible  albuminous  quantity  present,  in  an 
acidulated  solution  under  the  action  of  heat  and  electric  light  for  ten 
days,  have  given  the  following  results :  A  precipitation  of  modified 
nuclein  that  is  insoluble  in  the  acid  medium  and  a  propeptone 
moiety  that  remains  dissolved  in  the  solution.  I  wish  that  I 
were  prepared  at  this  time  to  give  you  the  ultimate  results,  but 
certain  conditions  will  not  permit.  The  purpose  of  this  paper  is 
only  to  urge  that  pepsin  solutions  should  be  kept  in  a  cool,  dark 
place,  because  of  their  sensitiveness  to  heat  and  light. 
