Comparative analysis of enzyme activity in human colostrum, milk, and serum.

Changes of enzyme activity in the colostrum, milk, and serum samples of 14 mothers were followed. For the enzyme assay, the colostrum and the milk samples were diluted, 1:10 and 1:5, respectively. The activity of the following enzymes were measured: lactate dehydrogenase (LDH); gammaglutamyl transpeptidase (GGT); aspartate aminotransferase (ASAT); alanine aminotransferase (ALAT); cholinesterase; alkaline, and acid phosphatase. Milk, LDH, ASAT, and ALAT activities did not change during the first four days of lactation, yet were significantly higher than the corresponding activities of serum. The activity of GGT and alkaline and acid phosphatase in milk showed a marked decrease by day 4 postpartum; however, the GGT stayed much higher than that of serum, while the activity of the other two enzymes decreased to the level of the serum. By contrast, as compared to the colostrum, the cholinesterase activity in the breast milk showed a significant increase.