The Development of Certain Enzymes and Iso-Enzymes During Normal Pregnancy

Abstract

During normal human pregnancy the maternal serum activity of
carboxypeptidase, leucine aminopeptidase, alanine aminopeptidase,
cystine aminopeptidase, γ-glutamyl transpeptidase, alkaline phosphatase,
glucose-6-phosphatase, 5-nucleotidase, n-acetyl-β-glucosaminidase,
n-acetyl-β-galactosaminidase and β-glucuronidase, have
been found to progressively increase. Dipeptidase and tripeptidase
were not found to increase during pregnancy.

A wide scatter of results was found during each week of pregnancy
which was due in part to poor reproducability of the techniques.
The enzyme assays were automated which improved the reproducability
and also afforded a means of quickly screening maternal serum enzymes
in all pregnant women attending the ante=natal clinic. With the
exception of γ-glutamyl transpeptidase which was found to originate
from liver the source of the increase in maternal serum enzymes is the
placenta.

Placental specific isoenzymes of leucine aminopeptidase, alanine
aminopeptidase, cystine aminopeptidase were characterized by electrophoresis
and by the use of activators and inhibitors. The isoenzymes
of liver also found present in pregnancy serum were found to increase
in maternal serum.

L-methionine was found to selectively activate the placental isoenzyme
and to inhibit isoenzymesof non=placental origin.

The apparent increase in glucose-6-phosphatase and 5-nucleotidase
was found to be due to the non-specific action of alkaline phosphatase
and results are presented which suggest that both enzymes are not
detectable during normal pregnancy.

The increase in n-acetyl-β-glucosaminidase and β-glucuronidase
was found immunologically to be of placental origin. Specific antienzyme
sera were produced in rabbits which showed that the placental
isoenzymes were immunologically distinct from that found in foetal and
maternal tissues.

In the light of the results obtained the estimation of certain
maternal serum enzymes or isoenzymes may be of clinical value as
a test of foeto=placental function.

Date of Award	1973
Original language	English