O. Fukushima et al., AN ENZYME-HISTOCHEMICAL INVESTIGATION OF CYSTEINE ENDOPROTEASE ACTIVITY IN CHICKEN BONE TISSUE, Acta histochemica et cytochemica, 27(3), 1994, pp. 245-249
Cysteine endoprotease activity was demonstrated in chicken osteoclasts
using an azo-dye method. The activity was also observed in cartilage
matrix where an active osteoclast attacked, but not in bone matrix. No
significant activity was seen in osteoblasts and osteocytes. The enzy
me hydrolyzed -phenylalanyl-L-arginine-4-methoxy-2-naphthylamide (Z-Ph
e-Arg-MNA), but not Z-Arg-Arg- nor Z-Ala-Arg-Arg-MNA. Furthermore, the
activity was dependent on mercaptoethylamine, an SH-reagent. A glutar
aldehyde-containing fixative was needed for demonstration of the activ
ity. There was no significant activity in 4% paraformaldehyde-fixation
samples, suggesting that this soluble enzyme protein might diffuse ou
t from the cell during histochemical prodecures in mild fixed sapmles.
This is the first report showing the presence of SH-reagent dependent
Z-Phe-Arg-MNA hydrolyzing activity in osteoclasts in vivo.