Background and Objective: Aminopeptidases
remove the amino acids from the N-terminal of proteins and peptides.
Aminopeptidase N (CD13) and leucine aminopeptidase
are involved in processing
and presentation of
pathogens to
immune cells. Also, enzyme activity in some viral infection and
tumors are high. In this study, the activity of CD13 in
serum with high
level of brucella antibody was measured. Due to the effect of protein,
cortisol,
bilirubin, and
total antioxidant
concentration on enzyme activity, these factors were also measured.   Materials and Methods: In this study, 37 sera
with high level
of brucella antibody and 30 sera from healthy subjects were collected and
enzyme activity
was measured by
spectrophotometry
using L-leucine
para-nitro-anilid
substrate. Protein
concentration
was determined by
the Bradford method, total antioxidant levels was assessed by
spectrophotometry
method,
cortisol level was measured by ELISA method and total bilirubin
was determined by calorimetric
method.   Results: CD13 activity
was not
significantly
higher in test
group than in
healthy subjects
and there was no
correlation between
enzyme activity
and
antibody titer
in test group. But
there was a
direct positive
and significant correlation between enzyme activity and cortisol
levels. Also, there was a
negative correlation between serum protein level with cortisol, bilirubin, and
total antioxidant. Also, there was a positive correlation between bilirubin and
total antioxidant in test group.    Conclusion: There were no
correlation between brucella antibody titer and CD13
activity. Also, factors
such as
protein,
reducing
substances,
bilirubin
and
cortisol
did not
interfere with
the
results achieved.