Demonstration of placental aminopeptidase isozymes by disc electrophoresis and its application to the forensic pregnancy test from blood stains.

Serum and placental aminopeptidase isozymes were characterized by means of disc electrophoresis. Human pregnancy sera exhibited three bands with leucine aminopeptidase (LAP) activity. The fastest moving LAP band was also present in nonpregnancy and foetal sera. The other two cystine aminopeptidase bands (CAP1 and CAP2), characteristic of pregnancy, were demonstrated in lysosomal extracts and hence suggested to be derived from the lysosomes of the placenta. These two CAP bands of lysosomal origin appeared in sera of pregnant women at different times during the course of gestation; CAP1 band in the 3rd month and CAP2 band in the 6th month. The information obtained from serum samples was applied to the medicolegal diagnosis of pregnancy from blood stains. Excess haemoglobin in blood stain extracts could be eliminated by subjecting them to a P-cellulose column. The results and their implications were discussed. This technique proved to be of practical use in the examination of blood stains up to periods of about 2 weeks after stain formation.