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.