Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Prothrombin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed1975

The control of prothrombin conversion. Kinetic control by mechanisms inherent in two activation pathways.

It is known that the activation of prothrombin to thrombin can proceed via two pathways: one initiated by the prothrombin-converting complex (factor Xa, factor V, phospholipid, and CA2+ ions) and the other initiated by the product, thrombin. A kinetic study has shown that the pathways do not proceed with equal ease under all conditions. At high levels of the converting complex, both go to completion: some prothrombin is always cleaved by thrombin, but the resulting intermediate is then activated to give quantitative conversion to thrombin. At slower rates of activation, the product-initiated pathway occurs to a relatively greater extent. Moreover, the intermediate then is not cleaved further but accumulates, so that the generation of thrombin is curtailed. The reason the intermediate is productive only at higher levels of activator may be partly that it is a poorer substrate for the converting complex than prothrombin. More importantly, the activity of the complex is also modulated by thrombin, which rapidly destroys the activity of factor V and factor Xa in a feedback reaction. These concerted controls ensure that prothrombin activation damps itself. Thus thrombin production occurs as a burst, the size of which is regulated by the amounts of factor Xa and factor V initially available.

Animals↗
PubMed1996

Dynamic features of prothrombin interaction with phospholipid vesicles of different size and composition: implications for protein--membrane contact.

The dynamics of prothrombin interaction with membrane vesicles of different size and composition was investigated to ascertain the impact of membrane surface characteristics and particle size on this interaction. Dissociation rates were highly sensitive to membrane composition and varied from about 20/s for membranes of 10% PS to 0.1/s for membranes of 50% PS. Overall affinity also varied by more than two orders of magnitude. Very small differences between prothrombin binding to SUV versus LUV were found. Association with large unilamellar vesicles (LUV of 115 nm diameter) was about 4-fold slower, when expressed on the basis of binding sites, than association with small unilamellar vesicles (SUV, 30 nm diameter) of the same composition. Both reactions proceeded at less than 25% of the collisional limit so that the differences were largely due to intrinsic binding properties. Vesicles of 325 nm diameter showed even slower association velocities. Dissociation rates from LUV were about 2-fold slower than from SUV. Again, these differences arose primarily from intrinsic binding properties. Dissociation conformed to a single first order reaction over a wide range of protein occupancy on the membrane. At very high packing density, the dissociation rate increased by about 2-fold. At equilibrium, prothrombin preferred binding to SUV over LUV by about 2-fold. This very small difference, despite substantial differences in phospholipid headgroup packing and hydrocarbon exposure, appeared inconsistent with an important role for protein insertion into the hydrocarbon region of the membrane. However, prothrombin-membrane interaction may arise from a series of interaction forces that have compensating features at equilibrium. The small differences in prothrombin binding to SUV versus LUV, together with differences in the number of protein binding sites per vesicle, were important to identify mechanisms of substrate delivery to the active site of the prothrombinase enzyme [Lu, Y., & Nelsestuen, G. L. (1996) Biochemistry 35, 8201-8209].

Binding, Competitive↗
PubMed2003

Role of factor V Leiden and prothrombin 20210A in patients with retinal artery occlusion.

PURPOSE: Retinal artery occlusion is a common vision-threatening disease. Among other risk factors, coagulopathies leading to a hypercoagulable state have been associated with retinal artery occlusion. Numerous studies have shown that two genetic variants, factor V Leiden and prothrombin 20210A, cause a procoagulant state. However, their role in the pathogenesis of retinal artery occlusion is still unclear. The purpose of the present study was therefore to investigate a possible association between factor V Leiden, prothrombin 20210A, and retinal artery occlusion. METHODS: In the present retrospective case-control study, we studied 136 patients with retinal artery occlusion and 136 age- and gender-matched control subjects. The presence of factor V Leiden and prothrombin 20210A alleles was determined by polymerase chain reaction. RESULTS: The prevalence of heterozygosity for the prothrombin G20210A variant did not significantly differ between patients and controls (three patients vs two controls, P=0.65). Distribution of factor V Leiden genotypes revealed no significant difference among the two groups (heterozygosity: eight patients vs 11 controls, P=0.47). As for other risk factors, arterial hypertension, a history of stroke and myocardial infarction were significantly more frequent in patients than in controls. CONCLUSION: Our data suggest that factor V Leiden and prothrombin 20210A do not play a major role in patients with retinal artery occlusion.

Adult↗
PubMed2003

Association of maternal and/or fetal factor V Leiden and G20210A prothrombin mutation with HELLP syndrome and intrauterine growth restriction.

This study was conducted to investigate the association of maternal and/or fetal factor V Leiden (FVL) and G20210A prothrombin mutation with HELLP syndrome. FVL and G20210A prothrombin mutation were determined using PCR. Sixty-three pregnant women, 36 of them diagnosed with HELLP syndrome, were included in the study. Overall, 68 children were born as a result of these pregnancies and blood sampling was possible in 28 out of 39 children from HELLP patients and 25 out of 29 children from the control women. The prevalence of a maternal FVL was elevated 2-fold in HELLP patients compared with the control women [six out of 36 (16.7%) compared with two out of 27 (7.4%); P =0.282]. None of the HELLP patients and only one woman in the control group was found to be positive for the G20210A prothrombin mutation (P =0.251). The fetal carrier frequency was four out of 28 compared with three out of 25 for FVL (P =0.811), and two out of 28 compared with one out of 25 for G20210A prothrombin mutation (P =0.629). Intrauterine growth restriction (IUGR) was significantly higher in fetuses found to be positive for a thrombophilic mutation (P =0.022). IUGR occurred in seven out of ten fetuses with a thrombophilic mutation compared with 11 out of 43 in fetuses without a mutation. The prevalence of FVL, but not of the G20210A prothrombin mutation, seems to be elevated in women with HELLP syndrome. A fetal thrombophilic mutation does not contribute significantly to the clinical features of the HELLP syndrome. Our results demonstrate a fetal contribution to IUGR. Fetal thrombophilic mutations may lead to placental microthrombosis, which consecutively could lead to a disturbed fetoplacental blood flow and thus cause growth restriction.

Adult↗
PubMed1999

Gly319 --> arg substitution in the dysfunctional prothrombin Segovia.

The molecular defect of a congenitally dysfunctional form of prothrombin, prothrombin Segovia, was identified in a patient with a severe bleeding tendency, reduced prothrombin coagulant activity, and normal antigen level. Nucleotide sequencing of amplified DNA revealed a G --> A change at nucleotide 7539 of exon 9 of the prothrombin gene. This resulted in the substitution of Gly319 by Arg. The proband was homozygous for this mutation, his father and brother were heterozygous. We surmised that the substitution, which occurs near the site of cleavage of prothrombin by factor Xa (Arg320-Ile321), altered the conformation of the protein making the cleavage site inaccessible.

Adult↗
PubMed2000

The risk of venous thromboembolism in family members with mutations in the genes of factor V or prothrombin or both.

Factor V Leiden and the G20210A mutation in the prothrombin gene are the most frequent abnormalities associated with venous thromboembolism. It is unknown whether the risks due to the presence of either mutation are of the same magnitude. We compared the prevalence and incidence rate of venous thromboembolism in relatives with either mutation or both. The finding of different rates might influence the strategies for primary prevention of thrombosis in carriers of these mutations. The study population included 1076 relatives of probands with the prothrombin gene mutation, factor V Leiden or both who underwent screening for inherited thrombophilia and were found to be carriers of single mutations or double mutations or who were non-carriers. The prevalence of venous thromboembolism was 5.7% in relatives with the prothrombin gene mutation, 7.8% in those with factor V Leiden, 17.1% in those with both mutations and 2.5% in non-carriers. Annual incidences of thrombosis were 0.13% [95% confidence interval (CI) 0.06-0.24], 0.19% (0.13-0.25), 0.42% (0.15-0.83) and 0.066% (0.03-0.11), respectively, and the relative risk of thrombosis was two times higher in carriers of the prothrombin gene mutation, three times higher in those with factor V Leiden and six times higher in double carriers than in non-carriers. The incidence of venous thromboembolism in carriers of the prothrombin gene mutation is slightly lower than that observed in carriers of factor V Leiden, whereas in carriers of both mutations it is two or three times higher. These findings suggest that lifelong primary anticoagulant prophylaxis of venous thromboembolism is not needed in asymptomatic carriers of single or double mutations. Anticoagulant prophylaxis seems to be indicated only when transient risk factors for thrombosis coexist with mutations.

Adolescent↗
PubMed2001

The risk of recurrent venous thromboembolism among heterozygous carriers of the G20210A prothrombin gene mutation.

The G20210A mutation in the prothrombin gene is associated with an increased risk of a first venous thromboembolic episode; few data are available about the long-term risk for recurrent venous thromboembolism and it is not known whether or not carriers of the mutation should be recommended lifelong anticoagulant treatment after the first thrombosis. We investigated 624 patients, referred for previous objectively documented deep venous thrombosis of the legs or pulmonary embolism, to determine the risk of recurrent thromboembolism in heterozygous carriers of the G20210A mutation in the prothrombin gene after the first episode of venous thromboembolism. After exclusion of other inherited (anti-thrombin, protein C, protein S deficiency and factor V Leiden) or acquired (anti-phospholipid antibody syndrome) causes of thrombophilia, 52 heterozygous carriers of the prothrombin mutation were compared with 283 patients with normal genotype. The relative risk for recurrent venous thromboembolism was calculated between groups using a Cox's proportional hazard model. The patients with the prothrombin mutation had a risk for spontaneous recurrent venous thromboembolism similar to that of patients with normal genotype (hazard ratio 1.3; 95% CI, 0.7-2.3). The circumstances of the first event (spontaneous or secondary) did not produce any substantial variation in the risk for recurrence. In conclusion, the carriers of the prothrombin mutation should be treated with oral anticoagulants after a first deep venous thrombosis for a similar length of time as patients with a normal genotype.

Adolescent↗
PubMed2002

Prothrombin A19911G and G20210A polymorphisms' role in thrombosis.

The prothrombin G20210A polymorphism, which correlates with the plasmatic prothombin levels, is the second genetic risk factor for deep venous thrombosis (DVT), although its prothrombotic role is mild. Recently, the prothrombin A19911G polymorphism, also associated with slight variations of the prothrombin level, has been suggested to modulate the thrombotic risk of the G20210A polymorphism in a preliminary study including few patients and controls. Our study evaluated the effect of the A19911G polymorphism in the arterial and venous thrombotic risk of the prothrombin 20210G/A genotype, analysing 204 consecutive DVT patients and 204 matched controls. Moreover, we analysed 213 carriers of the 20210G/A genotype (152 with DVT, 26 with arterial thrombosis and 35 healthy subjects) and 10 homozygous 20210 A/A carriers. We developed a simple method to simultaneously determine the genotype of both polymorphisms. In accordance with our case/control study, the A19911G polymorphism did not play a significant role in the development of DVT. Analysis of 120 20210 A alleles demonstrated a complete linkage disequilibrium with the 19911 A allele. These polymorphisms (alone or combined) did not modify the risk of arterial thrombosis. However, the 19911A/G genotype slightly increased the risk of developing DVT in carriers of the 20210G/A genotype (OR 3.34 vs 5.86), supporting that the prothrombin 19911 polymorphism could modulate the risk of the G20210A polymorphism in developing DVT.

Factor V↗
PubMed2002

Acquired activated protein C resistance is associated with the co-existence of anti-prothrombin antibodies and lupus anticoagulant activity in patients with systemic lupus erythematosus.

Venous thromboembolism (VTE) is one of the common manifestations in the anti-phospholipid (aPL) syndrome. We examined the levels of IgG antibodies (Abs) to beta2-glycoprotein I (beta2-GP I) and prothrombin, lupus anticoagulant (LA) activity, activated protein C resistance (APC-R), and factor V Leiden in 96 patients with systemic lupus erythematosus (SLE); 19 with VTE and 77 without VTE. Acquired APC-R, which was not found in any patient with the factor V Leiden mutation, was present in 33 (34.4%) out of the 96 patients with SLE. The presence of acquired APC-R was a strong risk factor for VTE. The SLE patients were divided into four groups according to the results of enzyme-linked immunosorbent assay (ELISA) and LA activity for each aPL Abs: ELISA+, LA+; ELISA+, LA-; ELISA-, LA+; and ELISA-, LA-. A significant association was observed between APC-R and the co-existence of anti-beta2-GP I Abs and LA activity or of anti-prothrombin Abs and LA activity. There was no association between APC-R and the presence of anti-beta2-GP I Abs, anti-prothrombin Abs, or LA activity alone. However, when multivariate logistical regression analysis was performed, it was clear that only the co-existence of anti-prothrombin and LA activity was a significant risk factor for APC-R. These findings indicate that the co-existence of anti-prothrombin Abs and LA activity may be an important factor in the pathogenesis of acquired APC-R in patients with SLE.

Activated Protein C Resistance↗
PubMedDate not supplied

[Incidence of thrombophilic factor V Leiden and prothrombin G20210A mutation in Perthes disease--a pilot study].

AIM: Thrombophilic mutations may play a role in the pathogenesis of the juvenile osteonecrosis of the femoral head, Perthes' disease. We investigated whether children with Perthes' disease have an increased incidence of mutations of factor V (Leiden) and prothrombin (G2O210A), which predispose to thrombosis. METHODS: For this pilot study, we analysed the data of twenty consecutive children (16 boys, 4 girls, mean age at diagnosis 6.4 years). According to Catterall's classification of severity, 2 children were in group 1, 7 in group 2, 8 in group 3, and 3 were in the most severe group 4. Mutations of factor V and prothrombin were identified in EDTA-blood by PCR amplification, digestion with restriction enzymes, and gel electrophoresis. RESULTS: Heterozygoty for the factor V mutation was detected in two children, for the prothrombin mutation in one child. Both results did not differ significantly from the incidence in Germany, which is 0.05 for factor V mutations and 0.04 for prothrombin mutations. CONCLUSIONS: For the presented group of children with Perthes' disease, we did not find an increased rate of factor V or prothrombin mutations compared to the natural incidence. In accordance to other recent studies, our results do not support a link between inherited thrombophilic mutations and Perthes' disease.

Alleles↗
PubMed2005

Ratcheting of the substrate from the zymogen to proteinase conformations directs the sequential cleavage of prothrombin by prothrombinase.

Prothrombinase catalyzes thrombin formation by the ordered cleavage of two peptide bonds in prothrombin. Although these bonds are likely approximately 36 A apart, sequential cleavage of prothrombin at Arg-320 to produce meizothrombin, followed by its cleavage at Arg-271, are both accomplished by equivalent exosite interactions that tether each substrate to the enzyme and facilitate presentation of the scissile bond to the active site of the catalyst. We show that impairing the conformational transition from zymogen to active proteinase that accompanies the formation of meizothrombin has no effect on initial cleavage at Arg-320 but inhibits subsequent cleavage at Arg-271. Full thermodynamic rescue of this defective mutant was achieved by stabilizing the proteinase-like conformation of the intermediate with a reversible, active site-specific inhibitor. Irreversible stabilization of intact prothrombin in a proteinase-like state, even without prior cleavage at Arg-320, also enhanced cleavage at Arg-271. Our results indicate that the sequential presentation and cleavage of the two scissile bonds in prothrombin activation is accomplished by substrate bound either in the zymogen or proteinase conformations. The ordered cleavage of prothrombin by prothrombinase is driven by ratcheting of the substrate from the zymogen to the proteinase-like states.

Binding Sites↗
PubMed1974

Vitamin K dependent modifications of glutamic acid residues in prothrombin.

A tetrapeptide, residues 6 to 9 in normal prothrombin, was isolated from the NH(2)-terminal, Ca(2+)-binding part of normal prothrombin. The electrophoretic mobility of the peptide was too high to be explained entirely by its amino-acid composition. According to (1)H nuclear magnetic resonance spectroscopy and mass spectrometry, the peptide contained two residues of modified glutamic acid, gamma-carboxyglutamic acid (3-amino-1,1,3-propanetricarboxylic acid), a hitherto unidentified amino acid. This amino acid gives normal prothrombin the Ca(2+)-binding ability that is necessary for its activation. Observations indicate that abnormal prothrombin, induced by the vitamin K antagonist, dicoumarol, lacks these modified glutamic acid residues and that this is the reason why abnormal prothrombin does not bind Ca(2+) and is nonfunctioning in blood coagulation.

Amino Acid Sequence↗
PubMed1975

Mitogenic activity of blood components. I. Thrombin and prothrombin.

When added to a culture medium of resting confluent chick embryo fibroblasts in the absence of serum, thrombin (EC 3.4.21.5) is able to stimulate DNA synthesis 12 hr later and to cause a substantial increase in cell number over a period of 4 days. As compared to thrombin, prothrombin exhibits low mitogenic activity. However, in the presence of purified Factor Xa (EC 3.4.21.6) and Factor V, prothrombin is converted to thrombin by "thromboplastin activity" supplied by the fibroblasts. Prothrombin, either purified or as a constituent of plasma or serum, may thus be considered to be a reservoir of mitogenic activity in tissue culture unless antithrombin is present in the culture medium in amounts sufficient to neutralize the thrombin formed. By use of a specific inhibitor of proteases, and by separation of prothrombin by absorption on BaSO4, we estimate that the potential mitogenic activity of prothrombin is approximately 30-50% of the total activity that can be obtained by treatment of fibrinogen-free plasma with thromboplastin. In addition to its mitogenic activity, thrombin can also stimulate the migration of cells. These experiments with thrombin illustrate that well-characterized proteases of blood can act as potent mitogens and suggest that they may play a role in the process of wound healing.

Animals↗
PubMed1995

Prothrombin activation by prothrombinase in a tubular flow reactor.

Thrombin production by the phospholipid-bound complex of blood clotting factors Xa and Va (prothrombinase) was studied in a tubular flow reactor. The inner wall of a glass capillary was coated with a phospholipid bilayer of 25% phosphatidylserine and 75% phosphatidylcholine. Prothrombinase was assembled on this bilayer by perfusion with a mixture containing an excess of factor Va (2 nM) and a limiting amount of factor Xa (1-100 pM), either in the absence or presence of prothrombin. The rate of assembly of prothrombinase in the presence of prothrombin appeared to be limited by the transfer rate of factor Xa to the phospholipid surface. A good agreement was found between the predicted mass transfer coefficient for factor Xa and the observed pre-steady state rate of thrombin production. The eventually obtained steady state rates of thrombin production were proportional to the prothrombin concentration and independent of the surface density of prothrombinase. The observed rate of thrombin production was in excellent agreement with the predicted mass transfer rate for prothrombin. Transport-limited prothrombin conversion was observed for prothrombinase densities exceeding 1 fmol/cm2, which corresponds to 0.05% occupation of available binding sites. The kinetic parameters of the reaction were determined at low prothrombinase densities (0.02-0.04 fmol/cm2). Even in this situation the Michaelis-Menten equation had to be corrected for substrate depletion near the catalytic surface. We hereto employed an accurate approximation of the mass transfer coefficient. The kinetic parameter kcat was 60 s-1 and the intrinsic Km had a surprisingly low value of 3 nM. Both parameters were not influenced by the wall shear rate.

Biotechnology↗
PubMed2000

The role of high molecular weight kininogen and prothrombin as cofactors in the binding of factor XI A3 domain to the platelet surface.

We have reported that prothrombin (1 microm) is able to replace high molecular weight kininogen (45 nm) as a cofactor for the specific binding of factor XI to the platelet (Baglia, F. A., and Walsh, P. N. (1998) Biochemistry 37, 2271-2281). We have also determined that prothrombin fragment 2 binds to the Apple 1 domain of factor XI at or near the site where high molecular weight kininogen binds. A region of 31 amino acids derived from high molecular weight kininogen (HK31-mer) can also bind to factor XI (Tait, J. F., and Fujikawa, K. (1987) J. Biol. Chem. 262, 11651-11656). We therefore investigated the role of prothrombin fragment 2 and HK31-mer as cofactors in the binding of factor XI to activated platelets. Our experiments demonstrated that prothrombin fragment 2 (1 microm) or the HK31-mer (8 microm) are able to replace high molecular weight kininogen (45 nm) or prothrombin (1 microm) as cofactors for the binding of factor XI to the platelet. To localize the platelet binding site on factor XI, we used mutant full-length recombinant factor XI molecules in which the platelet binding site in the Apple 3 domain was altered by alanine scanning mutagenesis. The recombinant factor XI with alanine substitutions at positions Ser(248), Arg(250), Lys(255), Leu(257), Phe(260), or Gln(263) were defective in their ability to bind to activated platelets. Thus, the interaction of factor XI with platelets is mediated by the amino acid residues Ser(248), Arg(250), Lys(255), Leu(257), Phe(260), and Gln(263) within the Apple 3 domain.

Amino Acids↗
PubMed2000

The Gla domain of human prothrombin has a binding site for factor Va.

The role of the Gla domain of human prothrombin in interaction with the prothrombinase complex was studied using a peptide with the sequence of the first 46 residues of human prothrombin, PT-(1-46). Intrinsic fluorescence measurements showed that PT-(1-46) undergoes a conformational alteration upon binding calcium; this conclusion is supported by one-dimensional (1)H NMR spectroscopy, which identifies a change in the chemical environment of tryptophan 41. PT-(1-46) binds phospholipid membranes in a calcium-dependent manner with a K(d) of 0.5 microm and inhibits thrombin generation by the prothrombinase complex with a K(i) of 0.8 microm. In the absence of phospholipid membranes, PT-(1-46) inhibits thrombin generation by factor Xa in the presence but not absence of factor Va, suggesting that PT-(1-46) inhibits prothrombin-factor Va binding. The addition of factor Va to PT-(1-46) labeled with the fluorophore sulfosuccinimidyl-7-amino-4-methylcoumarin-3-acetic acid (PT-(1-46)AMCA) caused a concentration-dependent quenching of AMCA fluorescence, providing direct evidence of a PT-(1-46)-factor Va interaction. The K(d) for this interaction was 1.3 microm. These results indicate that the N-terminal Gla domain of human prothrombin is a functional unit that has a binding site for factor Va. The prothrombin Gla domain is important for interaction of the substrate with the prothrombinase complex.

Amino Acid Sequence↗
PubMed2004

Binding of substrate in two conformations to human prothrombinase drives consecutive cleavage at two sites in prothrombin.

Thrombin formation results from cleavage of prothrombin following Arg(271) and Arg(320). Both bonds are accessible for cleavage, yet the sequential action of prothrombinase on Arg(320) followed by Arg(271) is implied by the intermediate observed during prothrombin activation. We have studied the individual cleavage reactions catalyzed by prothrombinase by using a series of recombinant derivatives: wild type prothrombin (II(WT)) contained both cleavage sites; II(Q271) contained a single cleavable site at Arg(320); II(Q320) and II(A320) contained a single cleavable site at Arg(271); and II(QQ) was resistant to cleavage. Cleavage at Arg(320) in II(Q271) could account for the initial cleavage reaction leading to the consumption of either plasma prothrombin or II(WT), whereas cleavage at Arg(271) in either II(Q320) or II(A320) was found to be approximately 30-fold slower. Equivalent kinetic constants were obtained for three of the four possible half-reactions. Slow cleavage at Arg(271) in intact prothrombin resulted from an approximately 30-fold reduction in V(max). Thus, the observed pathway of bond cleavage by prothrombinase can be explained by the kinetic constants for the four possible individual cleavage reactions. II(Q320) was a competitive inhibitor of II(Q271) cleavage, and II(QQ) was a competitive inhibitor for each reaction with K(i) approximately K(m). The data are inconsistent with previous proposals and suggest a model in which substrates for each of the four possible half-reactions bind in a mutually exclusive manner and with equal affinity to prothrombinase in a cleavage site-independent way. Despite equivalent exosite binding interactions between all four possible substrates and the enzyme, we propose that ordered bond cleavage results from the constraints associated with the binding of substrates in one of two conformations to a single form of prothrombinase.

Amino Acid Sequence↗
PubMed1981

A simplified procedure for purification of human prothrombin, factor IX and factor X.

A simplified procedure is described for the purification of prothrombin, Factor X and Factor IX in overall yields of 35-40% from pooled human plasma. The initial steps, which are common to prior purification techniques, include adsorption onto and elution from barium citrate, ammonium sulfate fractionation, and DEAE-Sephadex chromatography. The procedure differs from previous techniques in that the nest step, heparin-agarose chromatography, is carried out in a (sodium) citrate buffer, pH 7.5. These chromatographic conditions permit the separation of prothrombin, Factor X and Factor IX from each other, yielding fractions with apparent homogeneity in several electrophoretic systems. The additional chromatographic steps of earlier purification procedures are therefore unnecessary. The heaprin-agrarose column chromatographic conditions consistently resulted in the separation of human prothrombin in into two fractions in a ratio of approximately 4:1. Both fractions possess similar specific activity in a one stage prothrombin assay, and also activate at the same rate in a Factor Xa, Ca2+ and phospholipid system. Both fractions of prothrombin also comigrate in sodium dodecyl sulfate gel electrophoresis with an apparent Mr integral of 70,000.

Chromatography, Affinity↗