Behaviour of several enzymes of lysosomal origin in human plasma during pregnancy

The following enzymes of lysosomal origin were fluorimetrically determined in maternal plasma from the second to the ninth month of pregnancy at 1-mth intervals: β-d-N-acetylglucosaminidase (EC 3.2.1.30), β-d-glucuronidase (EC 3.2.1.31), β-d-glucosidase (EC 3.2.1.21), β-d-galactosidase (EC 3.2.1.22), α-d-galactosidase (EC 3.2.1.23), α-l-fucosidase (EC 3.2.1.51) and α-d-mannosidase (EC 3.2.1.24) (pH 4.0). As reference microsomal α-d-mannosidase (pH 5.7) was also studied. Thirty-eight healthy women, aged 18-37 yr, who had a normal pregnancy followed by normal parturition, were studied. All enzymes, with the only exception of β-D-galactosidase, showed a progressive and statistically significant increase of activity throughout pregnancy. At the end of pregnancy, the increase ranged from a maximum of 5.6-fold for β-d-N-acetylglucosaminidase to a minimum of 0.55-fold for α-d-mannosidase, pH 5.7. In the case of β-d-N-acetylglucosaminidase, the level at the fifth month of pregnancy was significantly higher than that at the third month, and from the sixth to the ninth month each level significantly differed from that of the month immediately preceding. After interruption of pregnancy (at the third month) and after normal delivery, the plasma level of some lysosomal enzymes, particularly of β-d-N-acetylglucosaminidase, sharply decreased to almost normal values. Therefore, the determination of some lysosomal enzymes, especially β-d-N-acetylglucosaminidase, can be suggested as predictive of a regular course of pregnancy. Women who developed gestational diabetes displayed a marked increase of the plasma levels of some lysosomal enzymes, particularly of β-d-N-acetylglucosaminidase, without any significant change of glycosylated haemoglobin, HbA1c. Thus, the plasma assay of this enzyme may constitute a valuable laboratory tool for monitoring gestational diabetes.