Purification to apparent homogeneity of inactive kallikrein from rat urine

Failure of the oxytocin-induced increase in secretion of urinary kallikrein in young spontaneously hypertensive rats

Urinary kallikrein excretion during oxytocin (OT) infusion were studied in anesthetized (sodium pentobarbital, 50 mg/kg, i.p.) young (4-weeks-old) spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). OT-infusion (30 nmol/kg/30 min) to WKY significantly increased urinary excretion of the active kallikrein from the basal levels (25.4 +/- 5.6 10(-2) x AU/15 min, n = 5) to 37.3 +/- 5.0 10(-2) x AU/15 min (P < 0.05, n = 5) and 50.7 +/- 17.1 10(-2) x AU/15 min (P < 0.05, n = 5) 15 and 30 min after the start of OT-infusion, respectively. In SHR, OT-infusion did not increase the urinary excretion of active kallikrein, but did decrease the urine volume and sodium excretion. The concentration of the active kallikrein in the kidney of WKY was not changed by OT-infusion, but that of SHR was slightly increased. The OT-infusion resulted in significantly higher concentrations of the active kallikrein in SHR kidney than in WKY kidney. These results suggest that less excretion of urinary kallikrein in SHR during OT-infusion may be attributable to a lower response in the secretion of kallikrein from the kidney.

Long-term infusion of kallikrein attenuates renal injury in Dahl salt-sensitive rats

We investigated whether long-term infusion of kallikrein would attenuate renal injury in salt-induced hypertension in Dahl salt-sensitive rats. A subdepressor dose of purified rat urinary kallikrein (700 ng/d IV) was infused by osmotic minipump for 4 weeks in male Dahl salt-sensitive rats fed a high salt (2% NaCl) diet. This dose did not affect the time-dependent elevation of blood pressure; however, urinary protein excretion was significantly decreased, and glomerular filtration rate was increased. These beneficial effects were reflected morphologically by an attenuation of glomerulosclerotic lesions and tubular injury seen in the hypertensive Dahl salt-sensitive rats. Kallikrein infusion increased urinary excretion of bradykinin and stimulated excretion of cyclic GMP, suggesting that the kallikrein-kinin-prostaglandin and nitric oxide axes were enhanced by rat urinary kallikrein infusion. The alterations induced by kallikrein infusion were potentiated by the concomitant administration of the angiotensin-converting enzyme inhibitor alacepril. These studies indicated that long-term replacement with rat tissue kallikrein attenuates renal injury in hypertensive Dahl salt-sensitive rats.

Pharmacological characterization of rabbit corpus cavernosum relaxation mediated by the tissue kallikrein-kinin system

1. The roles of the tissue kallikrein-kinin system and nitric oxide (NO) release in Phoneutria nigriventer venom-induced relaxations of rabbit corpus cavernosum (RbCC) smooth muscle have been investigated by use of a bioassay cascade. 2. Phoneutria nigriventer venom (10-30 micrograms), porcine pancreatic kallikrein (100 mu), rabbit urinary kallikrein (10 mu), bradykinin (BK, 0.3-3 nmol), acetylcholine (ACh, 0.3-30 nmol) and glyceryl trinitrate (GTN, 0.5-10 nmol) caused relaxations of the RbCC strips. Captopril (1 microM) substantially potentiated Phoneutria nigriventer venom- and BK-induced RbCC relaxations without affecting those elicited by GTN. 3. The bradykinin B2 receptor antagonist, Hoe 140 (D-Arg-[Hyp3,Thi5,D- Tic7,Oic8]-BK, 50 nM), aprotinin (10 micrograms ml-1) and the tissue kallikrein inhibitor, Pro-Phe-Aph-Ser-Val- Gln-NH2 (KIZD-06, 1.3 microM) significantly inhibited Phoneutria nigriventer venom-induced RbCC relaxations, without affecting those provoked by GTN and ACh. The B1 receptor antagonist, [Leu9]des Arg10BK (0.5 microM) and soybean trypsin inhibitor (SBTI, 10 micrograms ml-1) had no effect on Phoneutria nigriventer venom-induced RbCC relaxations. 4. The relaxations induced by Phoneutria nigriventer venom, porcine pancreas kallikrein, BK and ACh were significantly inhibited by N omega-nitro-L-arginine methyl ester (L-NAME, 10 microM) but not by D-NAME (10 microM). L-NAME did not affect GTN-induced relaxations. L-Arginine (300 microM), but not D-arginine (300 microM), significantly reversed the inhibitory effect of L-NAME. 5. Our results indicate that Phoneutria nigriventer venom activates the tissue kallikrein-kininogen-kinin system in RbCC strips leading to NO release and suggest a functional role for this system in penile erection.

Purification and characterization of human salivary-gland prokallikrein from recombinant baculovirus-infected insect cells

A full-length cDNA encoding human salivary-gland preprokallikrein was inserted into the baculovirus Autographa californica nuclear polyhedrosis virus downstream of the polyhedrin promoter. The gene was expressed in transfected Spodoptera frugiperda cells and the recombinant product secreted into the culture medium. By alternating anion-exchange chromatography and gel-filtration steps, twice repeated, prokallikrein was purified to homogeneity, which was confirmed by amino acid analysis and N-terminal sequence determination. The prepropeptide was processed correctly, including the removal of the signal peptide. The resulting proenzyme was found to be glycosylated, had a molecular mass of 35 kDa and an isoelectric point of 4.6. The yield of purified recombinant protein reached a level of 5 mg/l insect cell culture. After trypsin digestion of prokallikrein, the biological activity of the released kallikrein was demonstrated by its specific amidase, esterase and kininogenase activity. The expression and purification of prokallikrein, as described here, offers the opportunity to study the proenzyme activation through protein engineering techniques in detail.

Observation of tissue prokallikrein activation by some serine proteases, arginine esterases in rat submandibular gland

Two serine proteases, arginine esterases (esterases I and II) which showed the activity of tissue prokallikrein activation were identified in rat submandibular gland. These enzymes were separated from the homogenate of rat submandibular gland by two successive DEAE-cellulose chromatographies and were further purified and characterized. Esterases I and II were found to be identical with tonin and esterase B-like enzyme, respectively. Both enzymes activated rat urinary prokallikrein at near neutral pH. Esterase B-like enzyme activated rat urinary prokallikrein better than tonin.

Purification and partial characterization of a thiol proteinase activating prokallikrein from the rat kidney cortex

The rat kidney cortex contains at least three kinds of prokallikrein-activating proteinase, and among these the one with the highest molecular weight was purified by a procedure including chromatography on CM-cellulose, concanavalin A-Sepharose, organomercurial-Sepharose 4B and Sephadex G-100. The resulting preparation was apparently homogeneous, as assessed by SDS-polyacrylamide gel electrophoresis. The molecular weight was estimated to be 57,000. The optimal pH for the activation of prokallikrein by the preparation, termed activator I, was around 4.5. Activator I was inhibited by E-64, iodoacetate and leupeptin, but not by PMSF and phosphoramidon. In immunodiffusion analysis, the antiserum to activator I formed an immunoprecipitin arc with the extract from the kidney cortex or submandibular gland, but not with that from the pancreas. These results indicate that activator I is a thiol proteinase with a molecular weight of 57,000. A proteinase immunologically identical with activator I appears to be present in the submandibular gland.

Activation of inactive kallikrein in the rat kidney during low sodium intake

A method was developed to measure the protease responsible for activation of inactive kallikrein in the rat kidney. The renal protease was evaluated by incubating the purified rat urinary inactive kallikrein with the renal cortical extract in the presence of cysteine at pH 5.0. The renal cortical extract produced a dose- and time-dependent activation of the inactive kallikrein. Levels of the renal protease responsible for activation of inactive kallikrein remained unchanged with dietary sodium restriction. On the other hand, urinary excretion of total, active, and inactive kallikrein increased significantly during low sodium intake, with no change in the ratio of active to total kallikrein. These results suggest that low sodium intake stimulates the biosynthesis of inactive kallikrein but not the activation of this kallikrein precursor in the kidney.

The assay of glandular kallikrein and prekallikrein in human mixed saliva

The measurement of glandular kallikrein in biological fluids most often utilizes a synthetic substrate, H-D-valylleucylarginine-p-nitroanilide (S-2266), which assesses amidase activity. Although this substrate has reasonable specificity for glandular kallikrein, other tryptic-like proteases found in mixed saliva may also cause hydrolysis. The primary purpose of this study was to assess the accuracy of the use of this substrate for the measurement of glandular kallikrein in human mixed saliva. An additional objective was to determine the presence of prekallikrein in mixed saliva. The addition of soybean trypsin inhibitor (SBTI), which inhibits other tryptic-like enzymes but not glandular kallikrein, resulted in an approx. 30 per cent decrease in the hydrolysis of S-2266 by centrifuged mixed human saliva. A correlation of 0.918 was obtained between the biological assays for kinin release and amidase activity in 19 subject samples. Amidase activity increased following treatment of saliva with trypsin, indicating the presence of prekallikrein in human mixed saliva. It is concluded that S-2266 is an accurate substrate for the assay of glandular kallikrein in human mixed saliva; that the inclusion of SBTI in the assay mixture is needed to inhibit non-kallikrein proteases that may also hydrolyse the synthetic substrate; and that prekallikrein is present in mixed saliva. Thus any future studies of changes in the level of kallikrein in saliva may wish to consider the presence of both active and total levels of glandular kallikrein.

An improved method for the measurement of rat tissue kallikrein using a monoclonal antibody which recognizes only active enzyme

We have used a monoclonal antibody which recognizes active kallikrein to develop a method for measurement of inactive and active kallikrein in rat urine. The inactive kallikrein levels were calculated from the difference between values before and after trypsin pretreatment in the kallikrein direct radioimmunoassay. In this assay, the final dilution of ascitic fluid containing monoclonal antibody was 1:1.6 X 10(7) which gave 35% specific binding to 125I-labelled kallikrein, and the minimal detectable amount was 0.08 ng/tube. When inactive kallikrein was assessed by this method and a kininogenase assay in 23 randomly collected urines, a significant correlation was observed between the values obtained from the two assays (p less than 0.01). The regression line for this relation was similar to that observed between purified active kallikrein concentration and kininogenase activity. The active and inactive kallikrein excretion rates and the inactive/total kallikrein ratio in rats on normal sodium diet were 74.0 +/- 17.3 micrograms/day (m +/- SD), 82.8 +/- 14.4 micrograms/day and 53.1 +/- 7.1%, respectively. This method can now be applied to studies of prokallikrein activation.

Purification of inactive kallikrein from rat urine

An inactive kallikrein was purified from rat urine, and some of the properties of this enzyme were examined, in comparison with those of rat urinary kallikrein (RUK). The purified inactive kallikrein reacted with the antiserum against RUK and migrated slightly more slowly than RUK, on the immunoelectrophoresis. The molecular weights of the inactive kallikrein and RUK were estimated to be 44,000 and 38,000 by gel filtration, respectively. These results indicate that the rat urinary inactive kallikrein is immunologically identical with RUK, but this inactive enzyme has biochemical properties different from those of RUK, with respect to molecular weight and electrophoretical mobility.

Activation of urinary inactive kallikrein by an extract from the rat kidney cortex

Activation of purified urinary inactive kallikrein by an extract from the rat kidney cortex was investigated. The extract produced a dose-dependent activation of the inactive kallikrein and the optimum pH for this activation was 5.0. Marked depression of the activation was observed when the extract was pre-incubated with E-64, p-CMB and iodoacetate, but not with DFP, PMSF or pepstatin A. The molecular weight of the inactive kallikrein (Mr 44,000) was reduced to 38,000 by treatment with the extract, this molecular weight value being identical with that of urinary active kallikrein. These results indicate that the rat kidney cortex contains a protease catalyzing conversion of urinary inactive kallikrein into its active form, and that the protease has properties compatible with those of a thiol protease, but not of trypsin which has been used as a tool for the activation of urinary inactive kallikrein. The thiol protease is probably one of regulators of the kallikrein-kinin system in the kidney.

Immunological analysis of rat pancreatic prokallikrein activation

The present study shows that tissue kallikrein is present in rat pancreas as a proenzyme that can be converted by autolysis to a 38 000 Da active enzyme. The activation of pancreatic prokallikrein was examined by direct radioimmunoassay, enzymatic assays, active-site labeling with immunoprecipitation, and Western blot analyses. A monoclonal antibody (V1C3), which binds only active kallikrein, was used in a direct radioimmunoassay to monitor the appearance of the active enzyme. During a 22-h autolysis of pancreatic extract, a time-dependent increase in active kallikrein concentration paralleled the increase of kallikrein activities measured by both TosArgOMe esterase and kininogenase assays. The activation process was further analyzed by labeling the pancreatic extract with [14C]diisopropylphosphorofluoridate [( 14C]DFP) followed by immunoprecipitation with sheep anti-kallikrein antiserum. Pancreatic prokallikrein was not labeled by [14C]DFP; however, upon autolysis, a 38 000 Da active kallikrein can be labeled with [14C]DFP and increase in quantity with time. Western blot analysis, using a monoclonal antibody (V4D11) which recognizes both latent and active tissue kallikreins, identified a 39 000 Da pancreatic prokallikrein prior to autolysis and a 38 000 Da active kallikrein after 7 h of autolysis. The results indicate that the pancreatic prokallikrein exists as a 39 000 Da protein which may be converted to a 38 000 Da active kallikrein, indistinguishable from purified urinary, brain, spleen or submandibular gland kallikrein.