neurokinin-a and ubenimex

Topics: Animals; Animals, Newborn; Captopril; Drug Synergism; Evoked Potentials; gamma-Aminobutyric Acid; Glutamates; Glutamic Acid; Guanidines; Hydroxamic Acids; In Vitro Techniques; Kinetics; Leucine; Nerve Fibers; Neurokinin A; Protease Inhibitors; Rats; Rats, Wistar; Spinal Cord; Spinal Nerve Roots; Substance P; Tetrodotoxin; Thiorphan

A soluble tripeptidylaminopeptidase has been isolated from human post-mortem cerebral cortex by anion exchange, hydrophobic interaction and size-exclusion chromatography. From gel filtration studies the active enzyme can exist in both high molecular weight (M(r) > 10(6) and smaller forms. The enzyme hydrolyses Ala-Ala-Phe-7-amido-4-methylcoumarin with a pH optimum of around 7.5 and Km of 148 microM. It did not hydrolyse N-succinyl-Ala-Ala-Phe-7-amido-4-methylcoumarin, aminoacyl- or dipeptidyl-7-amido-methylcoumarins and was not inhibited by bestatin. The enzyme was inhibited by phenylmethylsulphonyl-fluoride, 3,4-dichloroisocoumarin, N-hydroxymercuriphenyl-sulphonic acid and N-ethylmaleimide showing that its activity is serine and cysteine dependent. The purified enzyme released tripeptides from several naturally occurring neuropeptides with quite broad specificity. Cholecystokinin octapeptide, angiotensin III and neurokinin A were the most rapidly hydrolysed. Peptides with Pro residues around the point of cleavage were not hydrolysed.

Topics: Amino Acid Sequence; Aminopeptidases; Angiotensin III; Cerebral Cortex; Chromatography; Chromatography, Gel; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Humans; Hydrogen-Ion Concentration; Leucine; Molecular Sequence Data; Molecular Weight; Neurokinin A; Neuropeptides; Serine Endopeptidases; Sincalide; Substrate Specificity

Myotropic effects of various peptides were measured in three isolated vessels, the dog carotid artery, the rabbit pulmonary artery and the rat portal vein in the absence and in presence of several peptidase inhibitors, in order to evaluate the interference by metabolism with the peptides' biological activities. After adequate controls, captopril (4.6 x 10(-6) mol/l), thiorphan (1.0 x 10(-6) mol/l), phosphoramidon (4.6 x 10(-6) mol/l), chymostatin (1 mg/l), bestatin (8.1 x 10(-6) mol/l) or bacitracin (1.4 x 10(-5) mol/l) were left in contact with the tissues for 20-40 min to inhibit tissue peptidases before measuring again the biological effects of the various peptides. In some experiments, mergetpa (5.4 x 10(-6) mol/l) was used. All peptidase inhibitors were inactive on their own and only captopril potentiated the effects of substance P, neurokinins, bradykinin and inhibited angiotensin I in two preparations, the dog carotid artery, the rat portal vein, and, excluding bradykinin, also in the rabbit pulmonary artery. Captopril and thiorphan significantly potentiated the maximal response of the rat portal vein to substance P and mergetpa inhibited completely the effect of bradykinin on the rabbit pulmonary artery. The present findings suggest that the most active proteolytic enzyme interfering with the biological effects of vasoactive peptides on three isolated vessels is the angiotensin-converting enzyme (kininase II).

Topics: Angiotensin II; Animals; Captopril; Carotid Arteries; Dogs; Female; In Vitro Techniques; Kinins; Leucine; Male; Muscle Contraction; Muscle, Smooth, Vascular; Neurokinin A; Neurokinin B; Portal Vein; Protease Inhibitors; Pulmonary Artery; Rabbits; Rats; Rats, Inbred Strains; Substance P

The effects of peptidase inhibitors were examined upon behavioural responses including scratch, bite and lick produced by intrathecal (IT) injection of substance P (SP) and neurokinin A (NK A) in mice. Phosphoramidon (0.002-2.0 nmol), an endopeptidase-24.11 inhibitor, simultaneously injected with SP or NK A, remarkably enhanced and prolonged SP- or NK A-induced behavioural response in a dose-dependent manner. The behavioural response to SP was significantly increased by 2.0 nmol of bestatin, an aminopeptidase inhibitor, but not by 1.0 nmol. Captopril, an angiotensin-converting enzyme inhibitor, was without effect on both tachykinin-induced responses. When phosphoramidon was injected together with bestatin and captopril which have no significant effect alone, SP- or NK A-induced behavioral response was significantly increased. These data suggest that endopeptidase-24.11 may be an important enzyme responsible for terminating of SP- or NK A-induced behavioral response at the spinal cord level.

Topics: Aggression; Animals; Behavior, Animal; Captopril; Dose-Response Relationship, Drug; Glycopeptides; Injections, Spinal; Leucine; Male; Mice; Mice, Inbred Strains; Neurokinin A; Substance P; Tachykinins