Biomedical subjects
S Schiffman
Publications and source records attributed to S Schiffman.
Changes in taste and smell: drug interactions and food preferences.
Explore the source record for details and available documents.
Purification and characterization of platelet factor XI.
Factor XI activity and antigen was purified about 300 fold from human platelets through chromatography on Con-A Sepharose, SP-Sephadex C-50, immobilized goat anti-factor XI, and SP-Sephadex. The partially purified platelet factor XI (Pt-XI) could be activated by activated factor XII generated in situ from single chain factor XI in a reaction requiring high molecular weight kininogen (HMWK) and a surface. Native Pt-XI migrated as a molecule of Mr = 245,000 on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) as identified by Western blotting. On reduction, Pt-XI appeared to have a Mr = 52,000. Neither form was affected by exposure to trypsin. Incubation of Pt-XI with purified factor XII, HMWK, and kaolin produced activated platelet factor XI clotting activity and, concomitantly, the generation over time of a new chain on reduced SDS-PAGE of Mr = 44,500. The coagulant activity of the activated form could be neutralized by diisopropyl flurophosphate (DFP). Incubation of the activated mixture with 3H-DFP followed by reduced SDS-PAGE showed the active site to be associated with a unit of Mr = 44,500. The adsorption domain as defined by adsorption to kaolin was localized to the Mr = 44,500 chain containing the active site. Hence, both active site and adsorption functions, properties of separate chains in plasma factor XI, reside in the same chain of Mr = 44,500 of platelet factor XI.
Enzymes of the contact phase of blood coagulation: kinetics with various chromogenic substrates and a two-substrate assay for the joint estimation of plasma prekallikrein and factor XI.
Kinetic constants (Km and kcat) of kallikrein and factor XIa for the chromogenic substrates H-D-L-prolyl-L-phenylanyl-L-arginine-p-nitroanilide (S-2302) and L-pyroglutamyl-L-propyl-L-arginine-p-nitroanilide (S-2366) were determined. The determined constants allow the use of S-2302 and S-2366 in an assay that leads to the joint estimation of factor XI and prekallikrein in activated plasma. The assay reports approximately 3.1 micrograms/ml factor XIa and 34.5 micrograms/ml kallikrein in kaolin-activated plasma (kaolin content 2 mg/ml). The dual-substrate amidolytic assay shows good correlation with the coagulant assay of both factors (0.92 with the prekallikrein assay and 0.98 with the factor XI assay). It is capable, through the joint estimation of factor XI and prekallikrein levels, of differentiating among plasma samples deficient in components of the contact phase of blood coagulation. Kinetic constants of factor beta-XIIa (factor XII fragment) for these substrates and for N-benzol-L-isoleusyl-L-glutamyl-glycyl-L-arginine-P-nitro ani lide (S-2222) were determined, and they allowed the assessment of the contribution of this factor to this assay and its estimation in the activated phase.
Effects of chemical modifications on the surface- and protein-binding properties of the light chain of human high molecular weight kininogen.
The light chain of kallikrein-cleaved human high molecular weight kininogen is solely responsible for its cofactor activity in blood clotting. Sequencing of the NH2-terminal region of the light chain reported herein identified the third kallikrein cleavage site of high molecular weight kininogen as Arg-437. The co-factor activity of high molecular weight kininogen consists of the capacity to bind to negatively charged surfaces and to factor XI or prekallikrein. Chemical modification of the histidines by either photooxidation or ethoxyformic anhydride affected the equivalent of 14-16 of 23 histidines available and resulted in over 90% loss in procoagulant activity. The modified protein had drastically reduced surface- and zinc-binding capacity, but it bound successfully to either factor XI or prekallikrein. In contrast, modification of two carboxyl groups, which led to approximately 80-90% loss of procoagulant activity, seriously compromised protein binding but left surface binding unaffected. All 3 tryptophans were modified at pH 4.0 with N-bromosuccinimide with a 70% reduction in procoagulant activity, but only 1 tryptophan was available for reaction at pH 7.35, resulting in a 50% loss in activity. Tryptophan modification at acidic pH affected protein binding but did not modify surface or zinc binding. Modification of both available tyrosine and 9 of 18 available lysine residues did not have a significant effect on the procoagulant activity of the light chain. These studies indicate that histidines participate in surface binding and that free carboxyl groups and tryptophan side chains are involved in binding of high molecular weight kininogen to other clotting factors.
Interaction of factor XI and sulfatide.
Explore the source record for details and available documents.
Interaction of factor XIa and antithrombin in the presence and absence of heparin.
We have studied the interaction between purified human factor XIa and antithrombin in the presence and absence of well-characterized preparations of heparin. The concentrations of hemostatic enzyme, protease inhibitor, and mucopolysaccharide were 5.76 X 10(-8) mol/L, 5.76 X 10(6) mol/L, and either 5.88 X 10(6) mol/L or 0, respectively. Kinetic investigation of this process using a tritiated factor IX substrate demonstrated that the pseudo first-order rate constants of this reaction in the presence and absence of heparin are approximately 1.0 min-1 and approximately 0.025 min-1, respectively. Thus, the rate of hemostatic enzyme-protease inhibitor complex formation is accelerated by about 40-fold in the presence of saturating levels of the mucopolysaccharide. These results were confirmed in a qualitative manner by directly monitoring the generation of factor XIa-antithrombin interaction product with sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis using an antibody population specific for the protease inhibitor.
Heparin-induced thrombocytopenia and thrombosis: detection and specificity of a platelet-aggregating IgG.
A 46-year-old female who died as a result of thrombocytopenia associated with multiple arterial occlusions and septicemia while on heparin therapy was found to have a platelet-aggregating factor present in several plasma samples and in a sample of serum. This factor was subsequently shown to be an IgG with aggregating properties toward normal platelets that were enhanced by, but not dependent on, the presence of heparin. Further studies showed that heparin was unlikely to have acted as a hapten in initiating the IgG production but that its role was significant in aggravating the ensuing arterial thrombosis. The necessity of substitution of heparin with alternative anticoagulant/antithrombotic therapy to avoid the worst sequelae of this potentially catastrophic syndrome is discussed.
Acquired factor XI inhibitors in two patients with hereditary factor XI deficiency.
Two patients with hereditary factor XI deficiency developed inhibitors following plasma transfusions. Neither had severe spontaneous bleeding. The patients' plasmas neutralized both factor XI in plasma, purified factor XI, and purified factor XIa. The inhibitor in both patients' plasmas adsorbed to Protein A-Sepharose. The inhibitors eluted from Protein A-Sepharose were partially neutralized by kappa and lambda light chain antisera indicating that they were polyclonal IgG antibodies. Both inhibitors markedly decreased adsorption of factor XI to glass surfaces. The cleavage of factor XI by trypsin was unaffected by the inhibitors. The lack of severe spontaneous bleeding in both of these patients strongly suggests that an alternate coagulation mechanism bypassing factor XI must compensate for this severe defect.
Phospholipids accelerate factor IX activation by surface bound factor XIa.
Activation of bovine factor IX by surface bound factor XIa which was generated either by activation of human citrated factor IX deficient plasma or a mixture of purified human factors XII, high molecular weight kininogen (HMWK) and XI in glass tubes, is accelerated by cephalin. Human brain cephalin in dilutions ranging from 1:5 to 1:500 was studied for its effect on the activation of factor IX in concentrations of 1.0 u/ml and 16 u/ml. Cephalin dilutions from 1:5 to 1:30 accelerated the activation of the concentrated factor IX sample two- to threefold. Protein cleavage of this factor IX sample in the presence of 1:30 cephalin occurred twice as fast as in the absence of cephalin. Activation of the dilute factor IX sample (1.0 u/ml) was most effectively accelerated by cephalin in dilutions from 1:30 to 1:250. In all experiments the presence of phospholipid led to an increased factor IX cleavage concomitantly with faster generation of factor IXa activity. The results demonstrate that phospholipids actively participate in blood coagulation at an earlier stage than previously described.
Role of charged groups in factor XI/XIa activity.
To elucidate the role of charged groups in expression of factor XI coagulant activity, the charged groups of purified human blood coagulation factor XI/XIa containing 125I-XI/XIa were derivatized: free amino groups by succinylation, guanido groups of arginine by reaction with phenylglyoxal hydrate, and free carboxyl groups by reaction with ethylenediamine. The modified proteins were tested for: 1) ability to adsorb to glass, 2) ability to be cleaved by trypsin or factor XII-high molecular weight kininogen, 3) coagulant activity. The amino group-modified factor XI had a significantly decreased ability to bind to glass; modification of arginine or carboxyl groups did not affect adsorption. Trypsin cleaved factor XI with modified free amino, guanido, or carboxyl groups. Factor XII-high molecular weight kininogen could cleave only the arginine-modified factor XI. Amino group-modified factor XI and carboxyl group-modified factor XI lost all their factor XI assay activity, whereas arginine-modified factor XI retained 50% of the original activity. Amino group-modified factor XI could not be activated by trypsin, but arginine-modified and carboxyl group-modified factor XI could be activated by trypsin to 50% of the original activity. Succinylation of the amino groups of factor XIa destroyed all its factor XIa activity. Arginine-modified and carboxyl group-modified factor XIa retained 50% of their factor XIa activity. We conclude that epsilon-amino groups are essential for adsorption; activation by factor XII-high molecular weight kininogen requires free amino and carboxyl but not guanido groups; free amino, carboxyl, and guanido groups in factor XIa all appear to be critical for interaction of factor XIa with factor IX.
Surface adsorption of factor XI. II. Evidence that different mechanisms are involved in binding to glass and plastic materials.
Blood coagulation factors XI and XIa possess binding site(s) for glass and plastics, located in the heavy chain of the molecule. To elucidate the nature of binding, adsorption and desorption properties of factor XI and XIa to different surfaces have been studied. Desorption experiments with high salt (2.4 M NaC1) suggest participation of ionic forces in the binding to glass. This is consistent with the decreased adsorption of factor XI (pI-9.0) to glass with increasing pH. The non-ionic detergent Triton X-100, which splits hydrophobic bonds, desorbs factor XI very well from plastics and partially from glass. The anionic detergent SDS, which will split hydrophobic as well as ionic bonds, is the most effective agent tested for the elution of factor XI from glass. We, therefore infer, that the binding of factor XI to glass is the combined effect of ionic and hydrophobic binding, whereas the adsorption of factor XI to plastics is primarily hydrophobic.
Kallikrein-like activity of crotalase, a snake venom enzyme that clots fibrinogen.
During the amino acid sequence determination of crotalase (EC 3.4.21.30), the thrombin-like enzyme from the venom of Crotalus adamanteus (eastern diamondback rattlesnake), we found that, in addition to the expected structural homology with bovine thrombin (EC 3.4.21.5), there was even greater homology with porcine pancreatic kallikrein (EC 3.4.21.8). In exploring further the similarities between crotalase and kallikrein, several striking observations were made. First, crotalase was rapidly and specifically inhibited by the tripeptide affinity labeling derivative prolylphenylalanylarginine chloromethyl ketone, which is known to be a specific inhibitor of kallikrein. Second, NaDodSO4/acrylamide gel electrophoresis revealed that crotalase cleaves the plasma kallikrein-susceptible bonds in human high molecular weight kininogen, producing an intermediate with procoagulant activity. Crotalase-catalyzed cleavage of high molecular weight kininogen also liberates kinin as evidenced by rat blood pressure bioassay. Finally, crotalase exhibits substrate specificity not only for the thrombin chromogenic substrate S-2238 but also for the kallikrein substrates S-2302 and S-2266. Interestingly, one of the other reactions catalyzed by plasma kallikrein, the activation of plasminogen, was not one of the activities exhibited by crotalase.
Contact activation of factor XI.
Factor XI is a circulating trace plasma protein composed of two similar or identical chains of about 80 000 daltons which upon activation undergo proteolytic cleavage. Recently, we have shown that trypsin activation leads to an active factor XI (factor XIa) which, on reduction, yields three chains of 46 000, 37 000 and 26 000 daltons. Herein, we re-evaluate the effect of contact activation of factor XI at an activating surface both in normal human plasma and in a mixture of purified factors XI, XII, and high molecular weight kininogen (HMWK). Mixtures were analysed by coagulant activity and by reduced sodium dodecyl sulphate polyacrylamide gel electrophoresis using [125I]factor XI. In the purified system, fully activated factor XI on reduction yielded chains of 46 000, 37 000 and 23 000 daltons. In contrast, factor XI activated by surface contact in plasma yielded on reduction only chains of 46 000 and 37 000 daltons in addition to some uncleaved 80 000 chain. We propose that factor XIa containing only 46 000 and 37 000 chains be designated factor XIa alpha, and that factor XIa containing the third chain of 23 000 daltons be designated factor XI a beta. Sequential elution of contact activated plasma factor XI revealed that factor XIa was attached to the glass surface through the 46 000 dalton chain.
Pseudo-factor-XI deficiency: effect of an inhibitor of factor XI adsorption to surface.
Recently we have described a normal plasma activity that modulates contact activation by inhibiting adsorption of factor XI to activating surfaces. Here we report the first identified case in which a patient has abnormal clotting tests due to an excess of a similar activity. The patient's plasma had a prolonged partial thromboplastin time and low apparent factor XI assay. His plasma prolonged the partial thromboplastin time of normal plasma and partially neutralized normal factor XI activity in vivo and in vitro. Analysis in dilute plasma revealed normal amounts of factor XI activity and antigen. Factor XI adsorption from plasma to activating surfaces was tested by adding a small amount of 125I-labeled purified factor XI to plasma, exposing the mixture to a glass tube or kaolin, and determining the amount of factor XI adsorbed to the surface. Whereas normal plasma and plasmas deficient in factor XII, factor XI, or Fletcher factor yielded about 4% adsorption to glass, factor XI adsorption from patient's plasma was less than 1%, indicating the presence of an adsorption inhibitor. This inhibitor did not affect factor XI activation or the activity of preformed factor XIa. It was not adsorbed by AI(OH)3 and was present in serum and the macroglobulin peak on gel filtration of the plasma through Sephadex G-200. The patient's history does not allow a definitive conclusion as to whether this inhibitor was associated with abnormal bleeding.
Human high molecular weight kininogen. Effects of cleavage by kallikrein on protein structure and procoagulant activity.
Explore the source record for details and available documents.
Surface adsorption of factor XI. Association of adsorption sites with the heavy chain of activated factor XI.
These experiments study surface adsorption of native and activated factor XI using purified radiolabelled human factor XI and trypsin activated factor XI. Both forms of factor XI adsorb not only to glass but also to polypropylene, polyethylene and polystyrene. Albumin (10 mg/ml) markedly reduces adsorption to plastics but not to glass. Sodium dodecyl sulfate prevents adsorption to all surfaces tested. Reduction of 125I-activated factor XI in the presence of sodium dodecyl sulfate yields labelled chains of molecular weight of about 46,000 (heavy chain), 37,000 (light chain) and a further breakdown product of about 26,000. Reduction of activated factor XI in glass or plastic in the absence of sodium dodecyl sulfate yields only light chain and breakdown product in solution; heavy chain is removed by adsorption. Therefore, we conclude that the adsorption site (s) in trypsin activated factor XI and presumably also in native factor XI is (are) located in the heavy chain subunit of the molecule.
Trypsin activation of human factor XI.
Human factor XI circulates as a zymogen composed of two similar or identical chains of Mr = 80,000. Upon activation either by trypsin or by blood-clotting proteins involving clotting factors XII and high molecular weight kininogen, it undergoes proteolytic cleavage in which the Mr = 80,000 chain reportedly is cleaved to a heavy and light chain of Mr of about 48,000 and 33,000, respectively. In these studies, we have reinvestigated trypsin activation of factor XI and demonstrate that trypsin-activated factor XI contains three chains of apparent Mr = 46,000, 37,000, and 26,000. Kinetic studies lead to the conclusion that the parent chain of Mr = 80,000 is cleaved into chains of Mr = 46,000 and 37,000. This cleavage is followed by a second nondestructive cleavage, most probably of the chain of Mr = 46,000, to yield the third product which migrates as a band of Mr = 26,000.