Human plasma kallikrein. A rapid purification method with high yield

Cleavage of the second component of complement by plasma proteases: implications in hereditary C1-inhibitor deficiency

EDTA plasma from patients with hereditary angioedema (HAE), the genetic deficiency of C1-inhibitor, when incubated at 37 degrees produces a kinin-like activity which can induce contraction of oestrus rat uterus. The second component of complement (C2) has previously been suggested to be the source of this kinin-like activity, with the implication that C2-kinin is a normal product of complement activation. Our results show that purified human C2 is cleaved rapidly to C2a and C2b when added to HAE plasma, but not normal plasma or plasma from a danazol-treated HAE patient. However, the addition to HAE plasma of C2 at 20 X normal plasma concentration had no effect on the kinin activity generated on incubation at 37 degrees. In the presence of soya bean trypsin inhibitor, the rate of C2 cleavage and products were unaltered but no kinin activity was generated. C2 was cleaved by purified C1s to C2a and C2b. Incubation of C2 with trypsin resulted in cleavage to C2a and C2b followed by more extensive cleavage of both C2a and C2b. Kallikrein cleaved C2 to C2a and C2b but plasmin had no effect on C2. In no case was kinin activity generated. When C2 was cleaved by C1s to C2a and C2b then incubated with trypsin, kallikrein, or plasmin, no kinin activity was generated: only trypsin cleaved the C2 fragments further. The results suggest that C2 is not the source of the kinin-like activity generated in hereditary angioedema plasma.

Generation of the bioactive kallikrein-derived fragment, C3d-k, by HANE-plasma

Recent studies have concluded that after complement activation the final physiologic degradation products of C3 are C3c and the fragment of relative molecular mass (Mr) 42,000 which contains the C3d and C3g domains and was therefore named C3d,g. Using fluorescent labelled C3b as a substrate, we have determined the putative C3d,g ('C3d,g') producing activity of both normal and hereditary angioneurotic oedema (HANE) plasmas. In normal plasmas, the rate of production of C3d,g was 1.0 +/- 0.2 X 10(-10) mol/ml/h and this activity was blocked by antibodies to I. In contrast, HANE, plasmas (deficient in C1INH) showed more than twice as much 'C3d,g' production as normal plasmas and both antibodies to I and kallikrein were required to inhibit this activity. Because of this result, a more sensitive gel system was employed to detect the Mr 42,000 peptide and two 'C3d,g' fragments of approximately equal intensity with Mr of 42,000 and 43,000 were defined. Incubation of purified kallikrein with labelled iC3b produced a C3d,g-like fragment, C3d-k, that aligned with the band of 43,000 Mr generated in HANE plasma. These results indicate that HANE plasma, in contrast to normal plasma, generates the bioactive C3d-k fragment. C1INH blocks the activities of kallikrein and C1s, and C3d-k generation in HANE plasma is probably secondary to the proteolytic activity of kallikrein.

Location of the inter-chain disulfide bonds of the third component of human complement

Location of the disulfide bonds connecting three polypeptide chains (alpha 3, 27kd; 2, 43kd; beta, 75kd) of C3c has been investigated by partial reduction with cysteine followed by alkylation with 14C-monoiodoacetic acid. Treatment of C3c with cysteine produced a partially reduced fragment, composed of disulfide-linked beta and alpha 3 chains. A single thiol residue was detected on the alpha 3 chain but not on the beta chain of the fragment, suggesting that the alpha 2 chain in C3c is linked through a single disulfide bond to the alpha 3 chain but not to the beta chain.

Variability in purified dysfunctional C1(-)-inhibitor proteins from patients with hereditary angioneurotic edema. Functional and analytical gel studies

C1(-)-inhibitor (C1(-)-INH) proteins from normal persons and members of eight different kindred with dysfunctional C1(-)-INH proteins associated with hereditary angioneurotic edema (HANE) were compared with respect to their inhibitory activity against purified preparations of C1s-, plasma kallikrein, activated forms of Hageman factor, and plasmin. Each dysfunctional C1(-)-INH protein showed a unique spectrum of inhibitory activity against these enzymes. Although none of the dysfunctional C1(-)-INH proteins significantly impaired amidolysis by plasmin, all but one inhibited activated Hageman factor. One purified dysfunctional C1(-)-INH (Ta) inhibited purified C1s- to a normal degree. Another C1(-)-INH (Za) had almost seven times as much inhibitory activity as normal C1(-)-INH against activated Hageman factor, but had decreased activity against C1s- and no activity against plasmin. Analyses of mixtures of plasmin and C1(-)-INH proteins in SDS gel electrophoresis revealed variability in the patterns of complex formation and cleavage of dysfunctional proteins after exposure to C1s- and plasmin. Some bound to plasmin and were cleaved, even though none significantly impaired the amidolytic activity of plasmin. Two were cleaved by C1s-, whereas neither normal or other dysfunctional C1(-)-INH were cleaved. Dysfunctional C1(-)-INH proteins from patients with HANE are thus heterogeneous in their inhibitory properties and there must be different structural requirements for the inhibition of the various plasma enzymes that can be regulated by normal C1(-)-INH. The data suggest that in addition to common sites of interactions between these proteases and C1(-)-INH, there are also points of contact that are specific for each protease. Genetic mutations leading to structural changes at some of these sites may have differing effects on the interaction between individual proteases and abnormal C1(-)-INH proteins. These alterations may allow these proteins to serve as probes for structural requirements for inhibitory actions of normal C1(-)-INH.

Human plasma alpha-cysteine proteinase inhibitor. Purification by affinity chromatography, characterization and isolation of an active fragment

Human plasma alpha-cysteine proteinase inhibitor (alpha CPI) was purified by a two-stage method: affinity chromatography on S-carboxymethyl-papain-Sepharose, and high-resolution anion-exchange chromatography. The protein was obtained as a form of Mr about 64 000 and material of higher Mr (about 100 000). In sodium dodecyl sulphate/polyacrylamide-gel electrophoresis with reduction, both forms showed a major component of Mr 64 000. An antiserum was raised against alpha CPI, and 'rocket' immunoassays showed the mean concentration in sera from 19 individuals to be 35.9 mg/dl. Both low-Mr and high-Mr forms of alpha CPI were confirmed to be sialoglycoproteins by the decrease in electrophoretic mobility after treatment with neuraminidase. alpha CPI was shown immunologically to be distinct from antithrombin III and alpha 1-antichymotrypsin, two serine proteinase inhibitors from plasma with somewhat similar Mr values. alpha CPI was also distinct from cystatins A and B, the two intracellular low-Mr cysteine proteinase inhibitors from human liver. Complexes of alpha CPI with papain were detectable in immunoelectrophoresis, but dissociated to free enzyme and intact inhibitor in sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The stoichiometry of binding of papain was close to 1:1 for both low-Mr and high-Mr forms. alpha CPI was found to be a tight-binding inhibitor of papain and human cathepsins H and L (Ki 34 pM, 1.1 nM and 62 pM respectively). By contrast, inhibition of cathepsin B was much weaker, Ki being about 35 microM. Dipeptidyl peptidase I also was weakly inhibited. Digestion of alpha CPI with bromelain gave rise to an inhibitory fragment of Mr about 22 000, which was isolated.

Enzymatic inactivation of human plasma C1-inhibitor and alpha 1-antichymotrypsin by Pseudomonas aeruginosa proteinase and elastase

Two major human plasma proteinase inhibitors, C1-inhibitor and alpha 1-antichymotrypsin, were enzymatically inactivated by Pseudomonas aeruginosa elastase and proteinase. Incubation of C1-inhibitor with the Pseudomonas enzymes at inhibitor/enzyme molar ratios of 1000:1 (elastase) or 22:1 (proteinase) resulted in cleavage of the 104 kDa intact inhibitor to an 89 kDa intermediate which retained full inhibitory activity against plasmin and plasma kallikrein. The intermediate was then cleaved to an 83 kDa inactive product. The initial non-inactivating cleavage of C1-inhibitor occurred in a region of the molecule readily accessible to limited proteolysis by both enzymes. The inactivating cleavage, however, occurred more readily with the elastase. alpha 1-Antichymotrypsin was inactivated by P. aeruginosa proteinase and elastase by limited proteolysis at inhibitor/enzyme molar ratios of 14 000:1. The 64 kDa intact inhibitor was cleaved to form an inactive 60 kDa product, and a low molecular mass peptide fragment was observed. No stable enzyme-inhibitor complexes were detected, and no random proteolysis of the inactivated inhibitors was noted, even after prolonged incubation. Catalytic inactivation of C1-inhibitor and alpha 1-antichymotrypsin by P. aeruginosa proteinase and elastase may contribute to the tissue damage and hemorrhagic lesions which occur during pseudomonal infections.

Reduced cofactor function of human high molecular weight kininogen induced by human plasma kallikrein

Most reports in the literature state that human plasma kallikrein does not destroy the capacity of human high molecular weight kininogen (HMrK) to function as a cofactor in the contact phase activation of factor XII. In the present work preparations of highly purified human plasma kallikrein that showed high plasminogen activator (PGA) activities rapidly reduced the cofactor function of human HMrK. Gel electrophoresis with SDS without reduction showed that all kallikrein preparations tested contained two protein bands, one major band with a Mr of about 83,000, and one weak band with a Mr of 80,000. The main band is probably identical with kallikrein I, which Levison & Tomalin (1982b), using Ac-Pro-Phe-Arg-OMe-HCl as substrate, found to be ten times more active (in terms of kcat/Km) than kallikrein II with Mr 3000 daltons lower. The rate of HMrK destruction in our experiments varied with the kallikrein preparation used, but assays of their hydrolytic activities against benzoyl arginine ethylester (BAEe) or the plasma kallikrein selective tripeptide substrate H-D-Pro-Phe-Arg-pNA (S-2302) did not discriminate between enzyme preparations with different HMrK-destroying capacities. Assay of PGA activities demonstrated a correlation between the level of PGA measured, and the HMrK-destroying capacity.

Activation of latent collagenase by serum proteinases that interact with immobilized immunoglobulin G

It has been previously observed that collagen destruction occurs in the vicinity of immune complexes present in articular cartilages of patients with rheumatoid arthritis. When IgG is covalently linked to Sepharose it behaves as if it has reacted with an antigen to form an immune complex, in that it binds the complement component C1 from human serum. Other serum components also interact with this matrix, though their interaction may not be specific for IgG. Two of these components were shown to possess proteolytic activity, one being kallikrein and the other having the properties of plasmin. Both of the activities could activate latent human collagenase. Whilst the binding of the plasmin activity is probably nonspecific, the binding of the kallikrein activity may be selective for IgG (although it is not certain whether this binding is direct or indirect via another molecule). These results therefore suggest that active proteinases such as plasma kallikrein may be selectively concentrated on immune complexes in vivo, where they may locally activate latent proteinases such as collagenase thereby initiating tissue destruction.

Survey of plant inhibitors of polymorphonuclear leukocyte elastase, pancreatic elastase, cathepsin G, cathepsin B, Hageman factor fragments, and other serine proteinases

Various flower bulbs and vegetable and legume seeds were tested for inhibitors of polymorphonuclear leukocyte elastase, pancreatic elastase, cathepsin G, cathepsin B, trypsin, alpha-chymotrypsin, Hageman factor fragments, plasma kallikrein, and plasmin. Calla bulbs contained a 33,000 dalton polymorphonuclear leukocyte elastase inhibitor and a 4,000 dalton cathepsin G inhibitor. Seeds of some members in the Cruciferae family, such as radish and broccoli, were found to contain one or more 2,500-4,000 dalton inhibitors which inhibited cathepsin G, trypsin, Hageman factor fragments, and plasmin, but not plasma kallikrein. These seeds also contained a 1,000 dalton cathepsin B inhibitor. The above inhibitors were probably polypeptides which inhibited proteinases by making an enzyme-inhibitor complex, with the exception of the cathepsin B inhibitor. These newly found inhibitors with their characteristic profiles of inhibition should be useful in biochemical and pathophysiological studies on granulocyte proteinases and enzymes of the coagulation and fibrinolytic pathways.

The purification and partial characterization of human salivary kallikrein

The major arginine esterase activity in human saliva has been purified. This enzyme lowers the blood pressure of a rabbit and produces kinins in acid treated dog plasma. It is therefore a kallikrein. The kallikrein has an unusual amino acid composition: aspartic acid and glutamic acid comprise 40% of the residues; the total number of basic residues is less than 5%; glycine and proline together make up more than 40% of the residues. The enzyme has a pI of 4.0 and an Mr of 27 000 as determined by dodecyl sulfate gel electrophoresis. On the other hand, sedimentation equilibrium data and the amino acid composition give an Mr value of only 9600. The enzyme could be a rather asymmetric molecule. The circular dichroism spectrum shows a minimum at 200 nm with [theta] = - 28 000 deg X cm2 X dmol-1. The spectrum suggests that the enzyme structure contains polyproline form II helix together with beta-turns. This structure is stable in the presence of dodecyl sulfate.

A comparison of the catalytic activities of human plasma kallikreins I and II

Subsites in the S2-S4 region [Schechter & Berger (1967) Biochem. Biophys. Res. Commun. 27, 157-162] were identified in human plasma kallikrein II (EC 3.4.21.8). Kinetic constants (kcat, Km) were determined for a series of seven extended N-aminoacyl-L-arginine methyl esters based on the C-terminal sequence of bradykinin (-Pro-Phe-Arg) or (Gly)n-Arg. With these substrates it was found that deacylation of the enzyme was rate-limiting. It was possible to infer that L-proline at residue P3 interacted with subsite S3 of the enzyme and L-phenylalanine at residue P2 interacts hydrophobically with subsite S2 in addition to hydrogen-bonded interactions with this subsite region. By comparison with the results of a similar study with human plasma kallikrein I, it is observed that although broadly similar subsite interactions occur between the two enzyme forms, the rate of deacylation of kallikrein II is approx. 35% of that observed for kallikrein I, and the latter form is up to ten times more active (in terms of kcat./Km) than kallikrein II.

A possible relationship between human plasma kallikreins I and II

Human plasma kallikrein I (EC 3.4.21.8; Mr 93 000) was found to undergo autolytic cleavage to form a protein resembling kallikrein II (Mr 85 000) plus a small peptide moiety. Conversion was found to be complete upon storage of kallikrein I solution at 4 degrees C for 7 days.

The kinetics of hydrolysis of some extended N-aminoacyl-L-arginine methyl esters by human plasma kallikrein. Evidence for subsites S2 and S3

Subsites in the S2-S4 region were identified in human plasma kallikrein. Kinetic constants (kcat., Km) were determined for a series of seven extended N-aminoacyl-L-arginine methyl esters based on the C-terminal sequence of bradykinin (-Pro-Phe-Arg) or (Gly)n-Arg. The rate-limiting step for the enzyme-catalysed reaction was found to be deacylation of the enzyme. It was possible to infer that hydrogen-bonded interactions occur between substrate and the S2-S4 region of kallikrein. Insertion of L-phenylalanine at residue P2 demonstrates that there is also a hydrophobic interaction with subsite S2, which stabilizes the enzyme-substrate complex. The strong interaction demonstrated between L-proline at residue P3 and subsite S3 is of greatest importance in the selectivity of human plasma kallikrein. The purification of kallikrein from Cohn fraction IV of human plasma is described making use of endogenous Factor XIIf to activate the prekallikrein. Kallikreins I (Mr 91 000) and II (Mr 85 000) were purified 170- and 110-fold respectively. Kallikrein I was used for the kinetic work.

Identification of plasma kallikrein as an activator of latent collagenase in rheumatoid synovial fluid

Rheumatoid synovial fluid contains an activator of latent collagenase from culture medium of pig synovium. The activator was purified by gel chromatography on Ultrogel AcA 44 and affinity chromatography on soybean trypsin inhibitor coupled to Sepharose 4B. The purified material was homogeneous on SDS-polyacrylamide gel electrophoresis with Mr 88 000. The activator had limited proteolytic activity against azo-casein, but showed amidase activity on Pro-Phe-Arg-NMec, Z-Phe-Arg-NMec, D-Val-Leu-Arg-NPhNO2 and D-Pro-Phe-Arg-NPhNO2, with an optimum at pH 8.0. Activity was completely inhibited by diisopropyl fluorophosphate, soybean trypsin inhibitor, leupeptin and Pro-Phe-Arg-CH2Cl, whereas lima bean trypsin inhibitor, Tos-Lys-CH2Cl, a specific inhibitor of factor XIIa from maize, EDTA and iodoacetate were not inhibitory. These properties of the activator suggested that it might be plasma kallikrein (EC 3.4.21.34), and the possibility was further examined. The activator was treated with [3H]diisopropyl fluorophosphate, and run in SDS-polyacrylamide gel electrophoresis with reduction; a radioautograph of the gel showed a pair of [3H]diisopropyl phosphoryl-labelled bands (Mr 36 000 and 34 000) identical to those obtained with authentic plasma kallikrein. Double immunodiffusion with monospecific antiserum against human plasma kallikrein confirmed the identification. This is the first demonstration of collagenase-activating activity of plasma kallikrein, and raises the possibility that activation of prokallikrein in the inflamed joint space may contribute to the disease process not only by the production of bradykinin, but also by activating latent collagenase.

The activation of the alternative pathway C3 convertase by human plasma kallikrein

Human plasma kallikrein can replace factor D for the activation of the alternative pathway C3 convertase of human complement. The factor B cleavage patterns by factor D and kallikrein are indistinguishable. The ability of kallikrein to cleave factor B is influenced by the magnesium ion concentration and the C3b concentration. Factor D is about ten-fold more effective on a molar basis, for the alternative pathway C3 convertase activation than is kallikrein. The physiological role of the action of kallikrein on the alternative pathway C3 convertase is discussed.

L-trans-Epoxysuccinyl-leucylamido(4-guanidino)butane (E-64) and its analogues as inhibitors of cysteine proteinases including cathepsins B, H and L

1. L-trans-Epoxysuccinyl-leucylamido(4-guanidino)butane (E-64) at a concentration of 0.5 mM had no effect on the serine proteinases plasma kallikrein and leucocyte elastase or the metalloproteinases thermolysin and clostridial collagenase. In contrast, 10 muM-E-64 rapidly inactivated the cysteine proteinases cathepsins B, H and L and papain (t0.5 = 0.1-17.3s). The streptococcal cysteine proteinase reacted much more slowly, and there was no irreversible inactivation of clostripain. The cysteine-dependent exopeptidase dipeptidyl peptidase I was very slowly inactivated by E-64. 2. the active-site-directed nature of the interaction of cathepsin B and papain with E-64 was established by protection of the enzyme in the presence of the reversible competitive inhibitor leupeptin and by the stereospecificity for inhibition by the L as opposed to the D compound. 3. It was shown that the rapid stoichiometric reaction of the cysteine proteinases related to papain can be used to determine the operational molarity of solutions of the enzymes and thus to calibrate rate assays. 4. The apparent second-order rate constants for the inactivation of human cathepsins B and H and rat cathepsin L by a series of structural analogues of E-64 are reported, and compared with those for some other active-site-directed inhibitors of cysteine proteinases. 5. L-trans-Epoxysuccinyl-leucylamido(3-methyl)butane (Ep-475) was found to inhibit cathepsins B and L more rapidly than E-64. 6. Fumaryl-leucylamido(3-methyl)butane (Dc-11) was 100-fold less reactive than the corresponding epoxide, but was nevertheless about as effective as iodoacetate.