Journal of Dental Research, Vol 63, 1067-1071, Copyright © 1984 by International & American Associations for Dental Research Online Journals
Properties of kininase in rat dental pulp
E. Maita, Y. Endo and Y. Ogura
A kininase, capable of degrading bradykinin, was partially purified from
the dental pulp of rats, and its properties were investigated.
Chromatography on both Sephadex G-200 and DEAE Sephadex A-50 columns gave a
single peak of kininase activity. The molecular weight of the enzyme,
estimated by gel filtration, was about 67,000, and the optimum pH for the
enzymatic reaction was about 7.5. The enzyme appears to contain a labile SH
group(s) that is essential for its activity, because CdCl2, HgCl2 (0.1 mM
each), and p-chloromercuric benzoate (0.05 mM) inhibited the enzyme
completely, while dithiothreitol retarded the loss of activity during
storage. Of various peptides tested, bradykinin was the substrate most
sensitive for the enzyme. The enzyme released several amino acids located
in the C-terminal regions of bradykinin--angiotensin I and neurotensin--but
only one C-terminal amino acid from des-Arg9--bradykinin and angiotensin
II. In contrast, the enzyme did not release any amino acids from substance
P, of which only the two amino acids in the N-terminal region are the same
as those of bradykinin, but its C-terminal is blocked by an amino group.
Although the enzyme was not so highly purified as to rule out the
contribution of other peptidases, these results suggest that the dental
pulp of rats may contain a single enzyme that degrades bradykinin, and the
enzyme may be a type of carboxypeptidase, differing from known kininases
from other animal sources.
