154 
Notes  on  Soy  Bean  Urease. 
Am.  Jour.  Pharm. 
March,  1920. 
by  Van  Slyke  and  CuUen.-^  They  found  the  optimum  temperature 
to  be  about  55°  C.  Thirty  minutes'  heating  with  water  at  60° 
was  without  effect,  30  minutes  at  70°  destroyed  about  one-fourth 
of  the  activity,  and  at  80°  there  was  complete  inactivation.  Hy- 
drolysis of  urea  by  urease  is  not  reversible. 
It  is  not  the  purpose  of  this  paper  to  review  all  of  the  literature. 
Commercial  preparations  of  purified  urease  are  now  on  the  market 
and  are  being  used  extensively  in  urine  analysis.  In  general  it 
appears  that  urease  is  most  abundant  in  seeds  of  high  protein  con- 
tent, particularly  in  the  Papilionaceae.  Its  absence,  however,  has 
been  reported  in  beans,  peas,  cowpea,  velvet  bean  and  sweet  pea. 
Incidental  to  a  study  of  various  seeds  to  discover  a  possible 
correlation  between  enzyme  activity  and  germinating  power,  the 
writer  had  occasion  to  compare  the  urease  content  of  a  number  of 
soy  beans  of  different  varieties  and  germinating  power.  The  only 
published  work  along  this  line  appears  to  be  that  of  Annett,^  who 
examined  six  varieties  of  soy  beans  which  he  describes  as  yellow, 
cinnamon,  chocolate,  spotted,  black  and  Rymbsa  Ktang.  His 
method  consisted  in  treating  10  g.  of  powdered  seed  with  100  Cc. 
distilled  water  in  the  presence  of  toluene  for  one  hour  at  room  tem- 
perature. Two  Cc.  of  the  extract  were  added  to  50  Cc.  of  a  i  per 
cent,  urea  solution,  the  mixture  kept  at  room  temperature  (about 
27°  C),  and  5  Cc.  aliquots  titrated  at  half -hour  intervals,  using 
methyl  orange  as  an  indicator.  The  six  varieties  showed  striking 
uniformity. 
In  the  present  work,  5  Gms.  of  each  sample  of  soy  beans  were 
ground  in  a  mortar  and  worked  through  a  40-mesh  sieve.  One- 
tenth  of  a  gram  of  the  powder  was  placed  in  a  small  Brlenmeyer 
flask,  15  Cc.  distilled  water  at  40°  added,  then  10  Cc.  of  a  i  per  cent, 
urea  solution,  after  which  the  flask  was  stoppei'ed  and  placed  in  a 
constant  temperature  bath  at  40°.  For  purposes  of  comparison  it 
was  decided  to  allow  the  reaction  to  proceed  for  a  period  of  time 
sufficient  for  the  hydrolysis  of  about  one-half  of  the  urea.  From 
the  following  table  it  will  be  seen  that  this  point  is  reached  in  about 
30  minutes.  At  intervals  of  ten  minutes,  one  of  a  series  of  flasks 
containing  the  above  mixture  was  removed  from  the  bath  and  ti- 
trated with  decinormal  hydrochloric  acid,  using  methyl  orange  as 
an  indicator.    A  uniform  blank  of  0.6  Cc.  was  deducted  in  each  case. 
5  Jour.  Biol.  Chem.,  19:  141-80,  1914. 
^  Biochem.  Jour.,  8:  449-52,  1914. 
