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PubMed1982

Correlation of hypotensive effect of plasma protein fraction with prekallikrein activator activity: a clinical study in patients having open-heart surgery.

We studied the hemodynamic responses to the administration of 20 ml of three protein solutions having different prekallikrein activator (PKA) activities in patients undergoing cardiac operation. PKA levels of the two plasma protein fraction (PPF) solutions studied were 193% and 60%, respectively, while that of the albumin solution was less than or equal to 3%. A significant correlation was found between the PKA activity of the test solutions and the decrease in systemic vascular resistance produced by the solutions during cardiopulmonary bypass and in the postoperative period. Vasodilatation was considerably more marked in the postoperative phase than during cardiopulmonary bypass. Since cardiac output increased simultaneously with the decrease in vascular resistance in the postoperative period, the hypotension observed did not fully reflect the degree of vasodilatation. In some patients, substantial vasodilatation was observed also after the administration of albumin solution with low PKA level. We conclude that although the PPF-induced vasodilatation correlates with the PKA activity of the solution, occasional hypotensive reactions are probably due to mechanisms other than those linked with increased PKA level.

Adult↗
PubMed1977

Coagulopathies.

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Afibrinogenemia↗
PubMed1995

Infusion of C1-inhibitor plasma concentrate prevents hyperamylasemia induced by endoscopic sphincterotomy.

Hyperamylasemia after endoscopic sphincterotomy is a common event, occurring in about 70% of cases. Clinical acute pancreatitis may also develop in 1% to 6% of cases. Previous attempts to prevent this reaction with inhibitors of exocrine pancreatic secretion (somatostatin and octreotide) provided conflicting and often disappointing results. Kallikrein is one of the proteases that sustain the inflammatory process in acute pancreatitis; the C1 inhibitor is the only physiologic inhibitor of the first component of the human complement cascade and is a major inactivator of kallikrein and Factor XII. Therefore, we tested the C1 inhibitor in the prevention of hyperamylasemia in 40 consecutive patients undergoing endoscopic sphincterotomy for common bile duct stones or benign papillary stenosis. They were given either C1 inhibitor (20 cases) or placebo (20 cases) before the procedure. Serum amylase levels were determined at baseline and 2, 4, 8, and 24 hours thereafter. Significant differences in serum amylase levels between groups were observed at 2 hours (p < .01), 4 hours (p < .0005), and 8 hours (p < .005) after sphincterotomy. The differences in amylase levels were also significant among the 24 subjects with pancreatic ductal filling (2 hours, p < .05; 4 hours, p < .005; 8 hours, p < .01) and the 9 patients with previous episodes of acute pancreatitis (4 hours, p < .05; 8 hours, p < .05; 24 hours, p < .05). The infusion of C1-inhibitor plasma concentrate resulted in a 50% increase in functional levels of C1 inhibitor (in the 8 cases for whom they were assayed), which persisted throughout the observation period.

Acute Disease↗
PubMed1998

Gamma interferon administration to patients with atopic dermatitis inhibits fibrinolysis and elevates C1 inhibitor.

Recombinant human gamma interferon was used to treat 10 atopic dermatitis patients. Recombinant gamma interferon was administered weekly for three consecutive days at 50 microg/M2 SQ for four weeks. All patients' dermatitis improved with recombinant gamma interferon therapy and plasma tumor necrosis factor-alpha levels rose with treatment. Recombinant gamma interferon treatment positively correlated with reduced total plasma fibrinolysis as measured by the fibrin lysis plate, plasmin-alpha2antiplasmin complexes, and tissue type plasminogen activator levels. Accordingly, plasminogen activator inhibitor levels increased. Treatment also was associated with a transient increase in thrombin-antithrombin III complexes. Recombinant gamma interferon resulted in a significant increase in C1 inhibitor antigen but not activity. Plasma prekallikrein, high molecular weight kininogen, and factor XII levels were not decreased. However, 5 of the 10 atopic dermatitis patients before therapy had circulating cleaved plasma high molecular weight kininogen detected on immunoblot, indicating prior kallikrein formation. The cleaved, circulating plasma high molecular weight kininogen disappeared in four out of the five original patients who were reexamined at one year after treatment. These combined data indicated that recombinant gamma interferon treatment reduced total plasma fibrinolysis. In untreated atopic dermatitis, circulating cleaved high molecular weight kininogen also may be a presenting manifestation.

Adolescent↗
PubMed2000

Singlet oxygen inactivates fibrinogen, factor V, factor VIII, factor X, and platelet aggregation of human blood.

Activated polymorphonuclear leukocytes participate in hemostasis. These phagocytes generate up to 5 mmol/l of oxidants of the HOCl- and chloramine-type. The present study shows, for the first time, that physiological concentrations of NaOCl or chloramines act as anticoagulants in human plasma. Prothrombin time, activated partial thromboplastin time, and thrombin time at chloramine concentrations greater than 1 mmol/l are prolonged proportional to the oxidant concentration. Plasmatic coagulation factors sensible to oxidation are fibrinogen, factor V, factor VIII, and factor X with a 50% effective dose of 2-3 mmol/l NaOCl or taurine-chloramine. Chloramines or chloramine-like agents (e.g., chloramine T(R) or vancomycin) also inactivate platelet aggregation (in whole blood or platelet-rich plasma) at an 50% effective dose of about 1.0 mmol. This irreversible oxidation of the hemostasis components is inhibited by addition of methionine, cysteine, ascorbic acid, or azide in 10-fold molar excess prior to oxidation. The oxy-radical inhibitors mannitol, superoxide dismutase, or catalase do not antagonize the action of NaOCl or chloramines. Therefore, the oxidant here involved has reaction characteristics of singlet oxygen (1O(2)), a nonradical, excited (i.e., light-emitting) oxidant. The hemostasis factors sensible to oxidation might dispose of oxidizable, for their function critical, methionine or cysteine residues. In conclusion, blood coagulation factors I, V, VIII, X and thrombocytes are sensible to nonradical oxidants of activated phagocytes. Via 1O(2) generation, polymorphonuclear leukocytes can generate a local pericellular zone of anticoagulation. The data suggest that the cell signal 1O(2) in physiological amounts is an antithrombotic agent.

Animals↗
PubMed2002

Zinc induces exposure of hydrophobic sites in the C-terminal domain of gC1q-R/p33.

Endothelial cells and platelets are known to express gC1q-R on their surface. In addition to C1q, endothelial cell gC1q-R has been shown to bind high molecular weight kininogen (HK) and factor XII (FXII). However, unlike C1q, whose interaction with gC1q-R does not require divalent ions, the binding of HK to gC1q-R is absolutely dependent on the presence of zinc. However, the mechanism by which zinc modulates this interaction is not fully understood. To investigate the role of zinc, binding studies were done using the hydrophobic dye, bis-ANS. The fluorescence intensity of bis-ANS, greatly increases and the emission maximum is blue-shifted from 525 to 485nm upon binding to hydrophobic sites on proteins. In this report, we show that a blue-shift in emission maximum is also observed when bis-ANS binds to gC1q-R in the presence but not in the absence of zinc suggesting that zinc induces exposure of hydrophobic sites in the molecule. The binding of bis-ANS to gC1q-R is specific, dose-dependent, and reversible. In the presence of zinc, this binding is abrogated by monoclonal antibody 74.5.2 directed against gC1q-R residues 204-218. This segment of gC1q-R, which corresponds to the beta6 strand in the crystal structure, has been shown previously to be the binding site for HK. A similar trend in zinc-induced gC1q-R binding was also observed using the hydrophobic matrix octyl-Sepharose. Taken together, our data suggest that zinc can induce the exposure of hydrophobic sites in the C-terminal domain of gC1q-R involved in binding to HK/FXII.

Binding Sites↗
PubMed1999

Bradykinin and its receptors in non-mammalian vertebrates.

The generation of bradykinin (BK) in blood by the action of the kallikrein-kinin system has been studied intensively in mammals but the system has received relatively little attention in non-mammalian vertebrates. The plasma of crocodilians and Testudines (turtles and tortoises) contains all the components of the kallikrein-kinin system found in mammals (prekallikrein activator, prekallikrein, kininogen, and kininases) and activation results in generation of [Thr6]-BK. Plasma of birds and snakes probably lacks a prekallikrein activator analogous to mammalian Factor XII but treatment with exogenous proteases (pig pancreatic kallikrein and/or trypsin) generates [Thr6, Leu8]-BK (chicken), [Ala1, Thr6]-BK (python) and [Val1, Thr6]-BK (colubrid snakes). The skins of certain frogs, particularly of the genus Rana, contain very high concentrations of BK-related peptides but their pathway of biosynthesis involves the action of cellular endoproteinase(s) cleaving at the site of single arginyl residues rather than by the action of the kallikrein-kinin system. Evidence for a prekallikrein activator in fish plasma is lacking but treatment with exogenous proteases generates [Arg0, Trp5, Leu8]-BK (trout and cod), [Trp5]-BK (bowfin and gar), [Met1, Met5]-BK (sturgeon). The cardiovascular actions and effects upon gastrointestinal smooth muscle of these peptides in their species of origin differ markedly. For example, intra-arterial injections of the native BK peptides into unanesthetized fish produce transient hypertension in the cod, complex depressor and pressor responses in the trout and bowfin and hypotension in the sturgeon. Pharmacological studies in snakes and fish and with the recombinantally expressed chicken BK receptor have demonstrated that the BK receptors in the tissues of non-mammalian vertebrates have appreciably different ligand binding properties from the well-characterized mammalian B1 and B2 receptors.

Amphibians↗
PubMed2001

Kringles of the plasminogen--prothrombin gene family share conformational epitopes with recombinant apolipoprotein (a): specificity of the fibrin-binding site.

Monoclonal antibodies directed against recombinant apolipoprotein (a) (r-apo(a)) lacking plasminogen-like KIV-2 repeats were used to identify structurally related conformational epitopes in various members of the plasminogen-prothrombin gene family. A number of procedures including a fibrin-binding inhibition immunoassay and surface plasmon resonance studies were used. Two antibodies (A10.1 and A10.4) recognised common conformational structures in r-apo(a), prothrombin, factor XII, plasminogen and its tissue-type and urokinase-type activators. In contrast, two other antibodies recognised specifically an epitope comprising residues of the lysine-binding site (A10.2) or close to it (A10.5) and inhibited the fibrin-binding function of r-apo(a) (IC(50)=36 pmol/l and 9.76 nmol/l, respectively). Interestingly, these antibodies distinctly recognised the elastase-derived fragments of plasminogen K4 (A10.2) and K1+2+3 (A10.5) without affecting plasminogen binding to fibrin. These results suggest that highly conserved conformational regions are common to various proteins of the plasminogen-prothrombin gene family and are in agreement with the concept that these proteins constitute a monophyletic group derived from an ancestral gene.

Antibodies, Monoclonal↗
PubMed1996

RETRACTED: The role of the protein C-thrombomodulin system and fibrinolysis during cardiovascular surgery: influence of acute preoperative plasmapheresis.

OBJECTIVES: To assess the benefits of withdrawn autologous plasma, the objective of this study was to investigate whether withdrawal of acutely performed platelet-rich or platelet-poor plasmapheresis allays changes in the protein C-thrombomodulin and fibrinolytic systems after retransfusion secondary to cardiopulmonary bypass (CPB). In addition, the study attempted to determine the influence of acute plasmapheresis (APP) on the protein C-thrombomodulin and fibrinolytic systems as well as on homologous blood consumption and perioperative blood loss in elective aortocoronary bypass patients. DESIGN: The investigation was scheduled as a prospective, randomized, unblinded study. SETTING: This single investigation was conducted in the Department of Anesthesiology and Intensive Care Medicine at a university in Germany. The study protocol was approved by the Ethics Committee of the hospital, and informed consent was obtained. PARTICIPANTS: Sixty male patients scheduled for elective coronary artery bypass grafting with extracorporeal circulation were included in the study. INTERVENTIONS: APP was performed between induction of anesthesia and incision, collecting either 10 mL/kg of autologous platelet-poor plasma (PPP patients, group 1; n = 20) or the same amount of platelet-rich plasma (PRP patients, group 2; n = 20). Patients of group 3 (n = 20) had no APP (control group). All patients were maintained on their usual regimen of cardiac drugs until the morning of surgery. To preserve hemodynamic stability and restore the intravascular oncotic pressure, the separated plasma was replaced by infusion of an equal amount of hydroxyethyl starch solution (HES) (6% HES, molecular weight 2 x 10(5), substitution rate 0.5%). In all operations, the same surgical procedure was chosen. For all patients, induction and maintenance of anesthesia were similar, consisting of weight-related doses of fentanyl (35 micrograms/kg), midazolam (0.65 mg/kg), and pancuronium bromide (0.15 mg/kg). The lungs of all patients were mechanically ventilated during the first 5 hours after the end of the operation. MEASUREMENTS AND MAIN RESULTS: All patients had serial coagulation studies including antithrombin (AT) III-activity, prekallikrein, factor XII, and immunologic tests such as thrombin-antithrombin III (TAT), fibrinopeptide A (FPA), protein C and S (PC and PS), thrombomodulin (TM), tissue-plasminogen-activator (t-PA), plasminogen-activator-inhibitor (PAI 1), fibrinopeptide B beta 15-42 (FPB beta 15-42), D-dimers, and hemoglobin and platelet counts determined intraoperatively and postoperatively. Chest tube drainage and transfusion requirements were recorded. APP had no negative effects on the quality of PPP and PRP plasma. The platelet count of the withdrawn plasma was 28 +/- 12 x 10(9)/L (PPP group) and 245 +/- 36 x 10(9)/L (PRP group). At the end of the operation (after retransfusion of autologous plasma) and on the morning of the first postoperative day, platelet counts were significantly higher (p > 0.05) in the PRP than in the PPP and control groups. Plasma concentrations of TAT and FPA increased (ranging from +185% to +340% from baseline values) and AT III-activity, PC, PS, and TM antigen decreased (ranging from -8% to -55% from baseline values) to a different extent for all three groups throughout CPB. t-PA-activity increased with a maximum at the end of CPB (PPP group, 6.9 +/- 1.5 IU/mL: PRP group, 3.8 +/- 0.8 IU/mL; control group, 10.9 +/- 2.8 IU/mL). Fibrin and fibrinogen degradation markers such as D-dimers and FPB beta 15 to 42 occurred in peak concentrations after neutralization of heparin by protamine. Only PRP patients showed baseline concentrations of coagulation parameters the next morning (p < 0.05). Total postoperative blood loss within the first 24 hours reached 482 +/- 273 mL (PRP group), 775 +/- 256 mL (PPP group), and 948 +/- 342 mL in the control group (p < 0.05).(ABSTRACT TRUNCATED)

Adult↗
PubMed1997

[Consequences for labile blood products of leukocyte depletion by whole blood filtration using the Leucoflex LST1 in-line filter. Evaluation of the Leucoflex LST1 filter].

The aim of this study is to evaluate the effects of whole blood filtration after a storage time of 20-24 hours at laboratory temperature using the in line filter Leucoflex LST1. The study concerns 49 blood donations in which we studied leukocyte depletion, proteins (IgG, IgA, IgM, haptoglobin, C3, C4), coagulation factors (fibrinogen, factors XII, XI, IX, VIII, V, proteins S and C, plasminogen, tPA, D-Dimers, PDF) at day 1, the parameters of conservation (ATP, 2-3 DPG, extra cellular potassium, haemolysis, pH) of red blood cell concentrates (RCCs) and bacteriological sterility at day 1 and 42. Despite a correct leukocyte depletion (mean depletion of 3.96 log), a 10 fold higher mean level of residual leukocytes/unit than with buffy coat poor RCC filtration (0.514.10(6) vs 0.051.10(6)) is observed. Moreover a lot of concentrates are not in accordance with French regulations (7/42 with more than 1.10(6) leukocytes/unit). The variation of the rates of IgG, IgA, IgM, haptoglobin, C4 and protein C is not significant. For the others there is a slight decrease with a mean level remaining in a physiological range. No sign of activation is noted. The sterility assays remain negative and the RCC conservation is not altered. In conclusion, even if the quality of the leukocyte depletion is not satisfactory in our study and has to be stated more precisely by multicenter studies, the whole blood filtration does not alter the quality of the derived components and allows us obtain RCC in a bigger volume and containing more haemoglobin than with the classical procedure after removing the buffy-coat [10].

Blood↗
PubMed1992

Interactions of factor XIII with fibrin as substrate and cofactor.

Factor XIIIa (a2') is a homodimeric transglutaminase that is formed via limited alpha-thrombin-catalyzed proteolysis of the platelet (a2) or plasma (a2b2) factor XIII zymogen in a reaction that results in proteolytic removal of a 37-aminoacyl residue peptide from the N-terminus of the a chains and exposure of the active-site thiol group in the resulting a' chains of factor XIIIa. In this study, we characterized interactions of factor XIII and factor XIIIa with fibrin, a natural substrate for factor XIIIa and a cofactor for the alpha-thrombin-catalyzed activation of plasma factor XIII. The carbamylmethyl derivatives of the active-site thiol group of platelet factor XIII (CMa2) and factor XIIIa (CMa2') were prepared, and their interactions with fibrin were measured. The enzyme-like derivative (CMa2') which contained nicked a' chains bound more tightly to fibrin (Kd = 2.1 microM) than did CMa2 (Kd = 14 microM), the platelet zymogen-like derivative with intact a chains, but the binding of each was weaker than the binding of plasma factor XIII zymogen (a2b2) to fibrin (Kd = 0.20 microM) under the same conditions. Saturation of fibrin with plasma factor XIII zymogen (a2b2) did not affect the binding of CMa2' to fibrin, suggesting that the plasma factor XIII zymogen (a2b2) and the active-site-modified form of factor XIIIa (CMa2') bind to separate, noninteracting sites of fibrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding, Competitive↗
PubMed1991

Surfactant protein B: disulfide bridges, structural properties, and kringle similarities.

The disulfide bridges in porcine hydrophobic surfactant protein B (SP-B) were determined. Results show that three intrachain bridges link half-cystine residues 8 and 77, 11 and 71, and 35 and 46, respectively. This gives SP-B an appearance of three loops, a central big loop surrounded by two smaller ones. In the major form of SP-B, the remaining half-cystine, Cys-48, is probably interchain-linked to its counterpart in another molecule, compatible with the existence of dimeric molecules. A minor fraction, with monomeric SP-B but also lacking free thiols, could be due to polypeptides having Cys-57 (instead of Leu in the major form) and hence an additional intrachain bond (Cys-48-Cys-57). Notably, one of the three intrachain bonds common to all SP-B molecules is analogous to one of the disulfide linkages in the kringle structure of complex serine proteases. SP-B and kringles are also similar in size and in positions of half-cystine residues. SP-B and the kringle of coagulation factor XII exhibit 26% residue identity. This structural similarity of SP-B to a binding domain could reflect functional homology, compatible with the notion that SP-B interacts with surfactant anionic phospholipids, which is also in agreement with an SP-B excess of basic residues. Finally, weak similarities between the perform of SP-B and complex serine proteases are also found. This has implications on further possible relationships between kringles, serine proteases, and antiproteases.

Amino Acid Sequence↗
PubMed1984

Active-site mapping of bovine and human blood coagulation serine proteases using synthetic peptide 4-nitroanilide and thio ester substrates.

A series of 14 tripeptide 4-nitroanilide substrates of the type Z-AA-Gly-Arg-NA and Z-AA-Phe-Arg-NA where AA = Ala, Asn, Glu, Lys, Phe, Pro, or Ser were used to map the S3 subsite of several serine proteases involved in blood coagulation. The enzymes studied included bovine thrombin, factor IXa, factor Xa, factor XIa, human beta-factor XIIa (factor XIIa fragment), and activated bovine and human protein C. Kinetic constants (kcat, KM, and kcat/KM) for the enzymatic hydrolysis of the substrates by each enzyme were determined and used to compare the relative reactivities of the individual enzymes. Most of the enzymes reacted with all the substrates, although a few showed considerable specificity. Human beta-factor XIIa showed the highest reactivity of all the coagulation proteases studied and was also very substrate specific (kcat/KM ranged over 470-fold). The best substrate was Z-Lys-Phe-Arg-NA with kcat/KM = 140 000 M-1 s-1. Activated bovine protein C (best substrate = Z-Ser-Phe-Arg-NA), factor Xa (best substrate = Z-Glu-Gly-Arg-NA), and thrombin (best substrate = Z-Lys-Gly-Arg-NA) were the group of enzymes that showed next highest reactivity toward the substrates. Activated bovine protein C, thrombin, and factor Xa displayed relatively little substrate specificity. Activated human protein C (best substrate = Z-Ser-Phe-Arg-NA) and factor XIa (best substrate = Z-Glu-Gly-Arg-NA) are moderately reactive enzymes. Activated human protein C is an extremely specific enzyme since it has such a large range of kcat/KM values.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Protection of human plasma kallikrein from inactivation by C1 inhibitor and other protease inhibitors. The role of high molecular weight kininogen.

High Mr kininogen increases the activation rate of prekallikrein by activated factor XII on a surface. The resulting serine protease, plasma kallikrein, Mr 88 000, is inhibited in plasma by C1 inhibitor, Mr 105 000. Since prekallikrein circulates in plasma with high Mr kininogen as a complex and a kallikrein-high Mr kininogen complex can be formed in purified systems, we studied whether the inhibition of kallikrein by C1 inhibitor was influenced by high Mr kininogen. With C1 inhibitor in excess, the inactivation of kallikrein followed pseudo-first-order kinetics. The second-order rate constant for the reaction was 1.7 X 10(4) M-1 s-1, and a kallikrein-C1 inhibitor complex, Mr 190 000 was identified on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Kallikrein and C1 inhibitor formed an irreversible complex without measurable prior equilibrium. The rate of this reaction was decreased by 50% in the presence of high Mr kininogen (1 unit/mL or 0.73 muM). Kinetic analysis indicated that this protection was the result of the formation of a reversible complex between kallikrein and high Mr kininogen, which had a dissociation constant of 0.75 muM. However, low Mr kininogen did not protect kallikrein from inactivation by C1 inhibitor. High Mr kininogen also protected kallikrein from inactivation by diisopropyl fluorophosphate. These findings suggest that the kallikrein-high Mr kininogen complex was formed by noncovalent interactions between the light chains of both kallikrein and high Mr kininogen.

Complement C1 Inactivator Proteins↗
PubMed1981

Mapping the active sites of bovine thrombin, factor IXa, factor Xa, factor XIa, factor XIIa, plasma kallikrein, and trypsin with amino acid and peptide thioesters: development of new sensitive substrates.

The subsite specificities of bovine factor IXa, factor Xa, factor XIa, factor XIIa, thrombin, plasma kallikrein, and trypsin were mapped with amino acid, dipeptide, and longer peptide thioester substrates. Each substrate contained a P1 Arg residue. The P1' residues included thiol residues which are analogues of valine, leucine, and isoleucine, respectively, and the P2 residue included 12 representative amino acid residues. Longer substrates with the sequence at the antithrombin III reactive site and at the zymogen activation site of various coagulation factors were also studied. The enzymatic hydrolysis of the thioesters was measured in the presence of 4,4'-dithiodipyridine which provides a very sensitive assay for the free thiol. The thioesters were excellent substrates for the coagulation factors studied, and the kcat/Km values for the best thioester substrates were higher than those previously reported for most of these enzymes. Thrombin and plasma kallikrein were the most active of the coagulation factors toward the thioester substrates. The best substrate for thrombin was Z-Gly-Arg-SCH2C6H5, although substrates containing proline in the P2 position were also quite effective. Some of the better substrates for plasma kallikrein had a P2 Phe or Trp residue. Factor IXa was the least reactive of the coagulation factors and hydrolyzed only four of the dipeptide thioesters. Substrates with bulky hydrophobic groups such as Phe or Trp in the P2 position were the most reactive with factor IXa. Factor Xa hydrolyzed all the thioester substrates tested, the most reactive being Z-Gly-Arg-SCH2C6H5. This is consistent with the fact that glycine and arginine are present in the P2 and P1 positions, respectively, of the factor Xa sensitive bonds in prothrombin which is the physiological substrate for factor Xa. Bovine factor XIa showed the least amount of specificity of the various coagulation factors and was quite reactive toward all of the thioester substrates. The most sensitive substrate for this enzyme was also Z-Gly-Arg-SCH2C6H5. Factor XIIa preferred the dipeptide with a P2 Phe, although the simpler thioester Z-Arg-SCH2CH(CH3)2 was more reactive. Trypsin hydrolyzed all of the thioester substrates at a high rate and showed little substrate specificity. With all enzymes studied, extension of the thioester substrate beyond P2 or the P1' thiol leaving group did not lead to an improvement in hydrolysis. Due to their high kcat/Km values and the ease of detecting the thiol leaving group, thioester substrates should be extremely useful for future studies of coagulation proteases.

Amino Acids, Sulfur↗