DETERMINATION OF N-ACETYL-BETA-DEUTERIUM-GLUCOSAMINIDASE AND CATHEPSIN-B ACTIVITY IN TROPHOTAENIAL PLACENTAL CELLS OF GOODEID FISHES

1. The trophotaenial placenta of the goodeid fishes is an externalized derivative of the hindgut. Trophotaenial epithelial cells transport s mall molecules or endocytose macromolecules, such as proteins, which s erve as nutrient substrates during gestation. 2. Trophotaeniae of the goodeid fishes Ameca splendens, Ilyodon furcidens, and Goodea atripinn is were analyzed for N-acetyl-beta-D-glucosaminidase and cathepsin B a ctivity, two enzymes of the endosomal-lysosomal system. 3. Synthetic c onjugates of 4-methylumbelliferone (4-methylumbelliferyl N-acetyl-beta -D-glucosaminide) and 7-amino-4-methylcoumarin yl-phenylalanyl-arginin e-4-methyl-7-coumarylamide) were used as substrates for the assays. 4. The specific activity of N-acetyl-beta-D-glucosaminidase in the troph otaeniae measured at 34.63 muU/mg protein for A. splendens, 84.81 muU/ mg protein for I. furcidens, and 67 muU/mg protein for G. atripinnis, was consistently less than in the control tissues (maternal liver and intestine). 5. In the case of cathepsin B, the specific activity in th e trophotaeniae measured at 91.23 mU/mg protein for I. furcidens, and 33.8 mU/mg protein for G. atripinnis, was less than in the intestine b ut greater than that of the liver for all the species of fish tested. 6. Cathepsin B activity was approximately 1000x greater than N-acetyl- beta-D-glucosaminidase in all three species. 7. There were no signific ant differences in the specific activity of either enzyme among the th ree species.