T-kinin release from T-kininogen by rat-submaxillary-gland endopeptidase K.
Submaxillary gland extracts have been fractionated to characterize the enzyme responsible for the T-kininogenase activity previously reported in this tissue [Damas, J. & Adam, A. (1985) Mol. Physiol 8, 307-316] and to know whether this activity could be of physiological relevance, since no enzyme reacting in catalytic amounts has been described so far to be able to release a vasoactive peptide from T-kininogen. The purified enzyme, provisionally called endopeptidase K, has an apparent Mr of 27,000 when not reduced prior to analysis but 21,000 after reduction and an acidic pI of 4.3 +/- 0.1. Antigenically, it is not related to tissue kallikrein. Upon incubation with purified T-kininogen it may induce a complete liberation of T-kinin from the precursor provided it is added in stoichiometric amounts. However, in parallel with the liberation of immunoreactive kinin, a proteolysis of T-kininogen is observed which is not restricted to the site of insertion of T-kinin as would be expected using a specific kininogenase. In agreement with these results, no change of the mean blood pressure was observed upon injection of endopeptidase K into the circulation of normal rats even if the amount of injected enzyme was up to ten times that required for tissue kallikrein to induce a significant fall in blood pressure. However, in spite of the large proteolysis induced by incubation with stoichiometric amounts of endopeptidase K, the total papain inhibiting capacity of T-kininogen as well as the value of the apparent inhibition constant, Ki, with this proteinase remained unchanged. Proteolytic fragments which retain cysteine-proteinase-inhibiting activity may therefore be released from T-kininogen by endopeptidase K more easily than immunoreactive kinin, thus emphasizing a prominent function of proteinase inhibitor or of proteinase inhibitor precursor for this molecule.
Gutman
N
N
Laboratoire de Biochimie, Faculté de Médecine, Université François Rabelais, Tours, France.
Moreau
T
T
Alhenc-Gelas
F
F
Baussant
T
T
el Moujahed
A
A
Akpona
S
S
Gauthier
F
F
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D005075:Biological Evolution; D001920:Bradykinin / Q000031:analogs & derivatives* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D019286:Endopeptidase K; D006868:Hydrolysis; D007122:Immunoelectrophoresis; D007704:Kininogens / Q000378:metabolism*; D051381:Rats; D012697:Serine Endopeptidases / Q000378:metabolism*; D013363:Submandibular Gland / Q000201:enzymology* / Q000378:metabolism
D000596:Amino Acids; D007704:Kininogens; C039065:T-kinin; D012697:Serine Endopeptidases; D019286:Endopeptidase K; D001920:Bradykinin