Tài liệu Báo cáo khoa học: Antiplasmin The forgotten serpin? doc

MINIREVIEW
Antiplasmin
The forgotten serpin?
Paul B. Coughlin
Australian Centre for Blood Diseases, Monash University, Prahran, Australia
Introduction
The fibrinolytic system is clearly important in human
biology and its major components are highly conserved
through vertebrate evolution. It is therefore very sur-
prising that it is so hard to find good evidence of
genetic anomalies in the fibrinolytic system commonly
associated with thrombotic or other diseases. Patients
deficient in plasminogen suffer from ligneous conjunc-
tivitis but not thrombosis [1,2] while there have been
no convincing reports of tissue plasminogen activator
(tPA) deficiency associated with thrombosis. On the
other hand mice rendered deficient in the fibrinolytic
proteases urokinase plasminogen activator (uPA), tPA
and plasminogen demonstrate significant phenotypes,
particularly when challenged with thrombotic or
inflammatory stimuli. Regulators of fibrinolytic pro-
teases should be important in thrombolysis and indeed
variation in the levels of plasminogen activator inhib-
itor-1 (PAI-1) appear to be important in the genesis of
atherothrombotic disease (reviewed in [3]). It may be
that these effects relate more to the role of PAI-1 in
regulating cell growth and migration rather than any
direct relationship to fibrinolysis. While there is no evi-
dence for variation in the level of antiplasmin (AP)
playing a part in thrombotic disease, complete defici-
ency causes a variable, but often severe, bleeding dis-

order [4].
Although at a clinical level it is unclear how import-
ant fibrinolytic abnormalities are in pathological clot
formation, it is well known that the rate and complete-
ness of clot lysis play a role in determining patient
outcomes. On the venous side of the circulation partic-
ularly the persistence of clot burden in leg veins is
Keywords
antiplasmin; fibrinolysis; plasminogen;
serpinF2
Correspondence
P. Coughlin, Australian Centre for Blood
Diseases, Monash University, Level 6,
Burnet Tower, Commercial Road, Prahran,
3181, Australia
E-mail:
(Received 9 May 2005, accepted 25 July
2005)
doi:10.1111/j.1742-4658.2005.04881.x
Much of the basic biochemistry of antiplasmin was described more than
20 years ago and yet it remains an enigmatic member of the serine protease
inhibitor (serpin) family. It possesses all of the characteristics of other
inhibitory serpins but in addition it has unique N- and C-terminal exten-
sions which significantly modify its activities. The N-terminus serves as a
substrate for Factor XIIIa leading to crosslinking and incorporation of
antiplasmin into a clot as it is formed. Although free antiplasmin is an
excellent inhibitor of plasmin, the fibrin bound form of the serpin appears
to be the major regulator of clot lysis. The C-terminal portion of anti-
plasmin is highly conserved between species and contains several charged
amino acids including four lysines with one of these at the C-terminus.

This portion of the molecule mediates the initial interaction with plasmin
and is a key component of antiplasmin’s rapid and efficient inhibitory
mechanism. Studies of mice with targeted deletion of antiplasmin have con-
firmed its importance as a major regulator of fibrinolysis and re-empha-
sized its value as a potential therapeutic target.
Abbreviations
AP, antiplasmin; PAI-1, plasminogen activator inhibitor-1; PEDF, pigment epithelium derived factor; serpin, serine protease inhibitor; tPA,
tissue plasminogen activator; TUG, transverse urea gradient; uPA, urokinase plasminogen activator.
4852 FEBS Journal 272 (2005) 4852–4857 ª 2005 FEBS
associated with post phlebitic symptoms and an
increased risk of recurrence [5] while residual pulmon-
ary artery emboli lead to pulmonary hypertension,
right heart failure and death.
Antiplasmin – the serpin
Like so many other molecular systems in biology,
fibrinolysis is organized on a surface, assembling and
orienting key components in close proximity. With
respect to intravascular clot the framework for assem-
bly is provided by fibrin polymers and fibrils (Fig. 1).
Both tPA and plasminogen bind fibrin leading to
enhanced rates of activation. Plasmin(ogen) is also
protected from inactivation by AP because the lysine
binding domains are occupied by fibrin. Conversely,
both PAI-1 and AP bind to fibrin during clot forma-
tion. PAI-1 binds via vitronectin which is incorporated
into the clot and AP is crosslinked to fibrin by Factor
XIIIa. Thus fibrin facilitates two opposing processes,
namely, the assembly and activation of profibrinolytic
enzymes and the binding of antifibrinolytic serpins.
How the balance between these pro- and antifibrino-

lytic factors plays out on the fibrin surface is unclear.
If there is an equilibrium between free and fibrin-
bound enzymes (tPA and plasmin) within the clot then
the inhibitors (PAI-1 and antiplasmin) are well placed
to regulate the unbound, unprotected proteases.
AP is present in plasma at a concentration of
approximately 70 lgÆmL
)1
(1 lm) and is the principal
physiological inhibitor of plasmin which is present in
plasma at a concentration of 2 lm [6]. It forms a con-
ventional serpin-enzyme complex with plasmin but its
activity is modified by the presence of N- and C-ter-
minal extensions that are unique among the serpin
family. The rate of association of AP with plasmin is
extremely fast at 2 · 10
7
mol
)1
Æs
)1
. This is comparable
to the rate of association of antithrombin and throm-
bin in the presence of unfractionated heparin. AP
interacts with plasmin in a two stage process. There is
an initial reversible association between the AP C-ter-
minal extension and the kringle domains of plasmin
followed by the formation of an irreversible serpin–
enzyme complex (reviewed in [7]).
AP possesses the conserved core structure of the

serpin family of proteins. Its functional importance
is highlighted by the highly conserved amino-acid
sequence between species. Human AP is 80% identical
with the bovine protein and is 74% identical with the
murine homolog. This sequence conservation includes
the reactive centre loop with the P
1
-P
1
¢ Arg-Met identi-
cal and strong conservation in both the N- and C-ter-
minal extensions. Phylogenetically AP is most closely
related to the noninhibitory serpin pigment epithelium
derived factor (PEDF) and these two are grouped
together in the F clade [8]. AP and PEDF are located
together on chromosome 17p13.3. AP and PEDF share
a common intron-exon structure except at the N-termi-
nus. AP has 10 exons [9] while PEDF has eight exons.
The intron–exon structure is conserved between the
A
B
C
Fig. 1. Schematic representation of the assembly of fibrinolytic pro-
teins. (A) In the absence of fibrin clot formation the principal fibrino-
lytic proteins are free in plasma. (B) Upon activation of coagulation
the fibrin clot forms. Antiplasmin is crosslinked by its N-terminus to
fibrin. tPA and plasminogen assemble on fibrin leading to the gen-
eration of plasmin. tPA can be inhibited by PAI-1 either in solution
or at the fibrin surface. Kringle domains on plasmin allow binding to
lysine residues on fibrin or alternatively in the C-terminus of anti-

plasmin. (C) While plasmin remains bound to fibrin it is relatively
protected from antiplasmin and fibrinolysis occurs. Antiplasmin is
crosslinked to the fibrin surface and is well placed to inactivate free
plasmin in this microenvironment.
P. B. Coughlin Antiplasmin – the forgotten serpin?
FEBS Journal 272 (2005) 4852–4857 ª 2005 FEBS 4853
two genes, except at the N-terminus where two addi-
tional exons are inserted between exons 2 and 3 of
PEDF corresponding to the AP N-terminal extension.
The intron–exon structure of AP is conserved between
Homo sapiens and Mus musculus in keeping with the
high overall sequence homology.
AP deficiency in humans has been well described
although only five variants have been characterized at
the molecular level [4]. AP Enschede is caused by an
alanine insertion at position 366 (between P
10
and P
11
)
lengthening the proximal hinge of the reactive centre
loop and causing the serpin to behave as a substrate
rather than inhibitor [10–12]. Reactive centre loop
length is known to be critical for correct inhibitory
function of serpins and insertions in other members
has resulted in similar disruption of function [13]. AP
V384M is a substitution in strand 1C just C-terminal
to the reactive center loop (P
8
¢) and is analogous to a

mutation in C1-inhibitor (V451M) which leads to
instability and polymerization. AP Okinawa (Glu149
deletion) disrupts the beginning of helix E and is there-
fore likely to cause malfolding and deficiency. The
other two antiplasmin variants are caused by frame
shift mutations.
Heterozygosity does not appear to have a clinical
phenotype but homozygous deficiency leads to a vari-
able but often severe bleeding disorder related to
excessive fibrinolysis [11,14]. In contrast, targeted dele-
tion of the AP gene in mice has been performed and
produces a remarkably normal phenotype with no
effect on fertility, growth, development or post-trau-
matic bleeding [15]. It was noted that AP
– ⁄ –
mice had
significant residual plasmin neutralizing activity (22%)
presumably related to other plasma protease inhibi-
tors. When the AP
– ⁄ –
mice were injected with pre-
formed clot to induce pulmonary embolism the
clearance of emboli from the lungs was markedly
enhanced in AP deficient animals. Surprisingly the
acceleration of clot clearance occurred irrespective of
whether the thrombi were derived from wild type or
AP
– ⁄ –
mice. In a separate report where pulmonary
emboli were induced in situ,AP

– ⁄ –
mice had a reduced
mortality compared to wild type (42% vs. 69%) [16].
The same experiment in plasminogen deficient mice
was universally fatal. When purified human AP was
infused into AP
– ⁄ –
mice the mortality was identical to
wild type.
N-terminal extension
There are differences in the literature with respect to
the amino-acid numbering of the AP protein
although there is general agreement that the signal
peptide cleavage occurs at the Asp-Met bond 27 resi-
dues from the translation start site giving rise to a
mature N-terminus of MEPL- (Fig. 2). In keeping
with the convention with other secreted serpins this
review will use numbering from the mature N-ter-
minal methionine. However, 70% of circulating AP
is truncated at the N-terminus by a further 12 amino
acids giving rise to the Asn form [17]. Even with
this additional 12 amino-acid deletion AP possesses
a 42 residue N-terminal extension before the start of
the first conserved secondary structural element of
the serpin core (the A-helix). During clot formation
the N-terminus of AP is crosslinked to fibrin by
Factor XIIIa. Gln14 appears to be the main target
for trans-glutamination as it is labelled preferentially
using the small molecule substrate [
14

C]methylamine
by Factor XIIIa and mutant serpin lacking Gln14 is
poorly crosslinked to fibrin [18]. The functional
importance of crosslinking to AP was illustrated by
Aoki et al. [19] in experiments using plasma from
patients deficient in AP. It was shown that clot lysis
was accelerated and when AP was added to plasma
the rate of lysis was related to the amount of inhib-
itor crosslinked to the clot and was relatively insen-
sitive to free AP.
Fig. 2. Homology of human, bovine and murine antiplasmin at the N- and C-terminus. Homology diagram showing conservation of the first 54
residues of the antiplasmin N-terminus and final 55 residues at the C-terminus. Signal peptide cleavage gives rise to the mature N-terminus
(MEPL-). Further cleavage at position 12 (.) gives rise to the Asn form of the protein. The preferred target for trans-glutamination is Gln14
(m). The conserved Cys43 situated 12 residues before the A-helix is shown (n). Conserved residues are shown with a grey background.
Antiplasmin – the forgotten serpin? P. B. Coughlin
4854 FEBS Journal 272 (2005) 4852–4857 ª 2005 FEBS
As noted above, AP exists in two forms at the
N-terminus and this affects susceptibility for crosslink-
ing to fibrin. Lee et al. [20] showed that the Asn form
of AP was crosslinked to fibrin 13 times faster than
the native Met form. They were also able to demon-
strate a protease in plasma capable of cleaving AP at
position 12 to generate the Asn form although the
reaction appeared to be slow. It remains to be seen
whether this represents the physiological mechanism
for modifying the N-terminus.
Some attention has been paid to the potential for
disulfide bond formation in AP. The serpin has four
cysteine residues at positions 43, 76, 116 and 125. By
comparison bovine AP has three cysteines (lacking 76)

and the mouse has only two (lacking 76 and 125). It
was originally reported that human AP contained two
disulfide bonds [21] but Christensen et al. [22] demon-
strated that the protein contains free thiols and identi-
fied a single bond between residues 43 and 116. This
result is much more consistent with the nonconserva-
tion of residues 76 and 125. From a structural point of
view Cys43 lies approximately 12 amino acids N-ter-
minal to the A-helix, the first conserved secondary
structural element of the serpin (Fig. 2). Cys116 is
located in the C-D interhelical region although it is dif-
ficult to be certain of the precise structural location as
this is an area of marked variability between serpins.
In particular there is very little similarity between AP
and its closest relation PEDF, for which there is a
crystal structure, in this region. Cysteine residues in
the C-D interhelical region are relatively uncommon
with the exceptions being the ovalbumin serpins PAI-2,
bomapin, PI-8, ovalbumin and gene-Y [8]. It has
been proposed that Cys79 in the PAI-2 C-D interheli-
cal loop can form a disulfide bond with Cys161 at the
bottom of the F helix and that this bond leads to
opening of the A b-sheet and consequent polymeriza-
tion [23,24]. In addition angiotensinogen possesses a
highly conserved cysteine residue in the C-D inter-
helical region. Interestingly this cysteine has also been
shown to be disulfide bonded to a cysteine in the
N-terminal region suggesting that this is a mechanism
for imposing structural constraint on the N-terminus
of serpins with possible functional significance [25].

Christensen et al. [22] compared native AP to the
reduced and alkylated form of the protein and exam-
ined structural stability by transverse urea gradient
(TUG) gels and the association rates with trypsin. No
difference was found but the sensitivity of TUG gels
would be inadequate to detect the relatively small
effect expected from an additional disulfide bond not
involving core serpin secondary structural elements.
The disulfide bond from Cys43 to Cys116 is most
likely to position the N-terminus at the ‘lower’ end of
the protein so that after crosslinking to fibrin the react-
ive centre loop at the ‘top’ end of the molecule would
be optimally exposed for interaction with plasmin.
C-terminal extension
AP possesses a C-terminal extension of 55 amino acids
beyond the conserved proline at the end of strand 5 of
b-sheet B. This is strongly conserved between species
with 67% identity between human and bovine and
61% identity between human and mouse (Fig. 2). It
does not show any similarity to other proteins but con-
tains a number of conserved charged amino acids
including a C-terminal lysine which is believed to asso-
ciate with the lysine-binding domain of plasmin. The
interaction between AP and microplasmin (lacking
kringles with lysine binding domains) is 30–60 times
slower than with plasmin (6.5 · 10
5
m
)1
Æs

)1
vs. 2 · 10
7
mol
)1
Æs
)1
) [26]. Frank et al. [27] studied the interaction
of recombinant AP C-terminal fragment (Asn398-
Lys452) and demonstrated high affinity binding to
recombinant plasmin kringles 1 and 4. If the C-ter-
minal lysine was deleted then the affinity decreased five
fold indicating that, while Lys452 was important, other
residues contribute significant binding capacity. They
proposed a sequential zipper-like model for the inter-
action of the AP C-terminus with the plasmin kringles.
Surprisingly, approximately 40% of circulating AP
binds plasmin slowly [28]. Sasaki et al. [29] made the
same observation and demonstrated that the slow form
was truncated at the C-terminus by at least the final 26
amino acids. When this observation is taken together
with the fact that 70% of antiplasmin is in the Asn12
cleaved form which is the best substrate for crosslink-
ing to fibrin, it implies that only 40% of total circula-
ting protein is optimal for both incorporation into clot
and rapid inhibition of plasmin.
AP as a therapeutic target
AP is clearly a key regulator of the principal clot lys-
ing enzyme plasmin and is therefore a rational thera-
peutic target. The domains within AP that are

accessible to manipulation are the N- and C-terminal
extensions and the reactive centre loop. Lee et al. dem-
onstrated that the addition to plasma of mutant AP
(P
1
Arg-Ala), which has no plasmin inhibitory activity,
accelerated clot lysis by competitively crosslinking to
fibrin [30]. Similarly, when a monoclonal antibody
which bound and blocked the AP reactive centre loop
was added to plasma it dramatically enhanced the
effectiveness of tPA induced clot lysis [31]. Other
P. B. Coughlin Antiplasmin – the forgotten serpin?
FEBS Journal 272 (2005) 4852–4857 ª 2005 FEBS 4855
approaches to therapeutic manipulation of AP are to
block either the N- or C-terminal extensions which are
required for crosslinking to fibrinogen and interaction
with plasmin, respectively. Kimura et al. [32] showed
that when plasma was clotted in the presence of
12-mer synthetic N-terminal AP peptide that there
was a marked enhancement of spontaneous and
tPA-induced clot lysis. This corresponded to inhibition
of AP incorporation into the clot and was not seen in
plasma deficient in either AP or Factor XIII.
The C-terminal portion of AP inhibits fibrinolysis in
two ways; it competes with lysine residues in fibrin for
plasminogen binding and it binds directly to plasmin
kringle domains thereby dramatically enhancing the rate
of AP inhibition. Lysine analogues such as EACA and
tranexamic acid compete for binding at the plas-
min(ogen) kringles impairing interaction of plasmin to

both AP and fibrin. In vivo the dominant effect of these
analogues is antifibrinolytic presumably because the ant-
agonism of interaction with fibrin is more important. By
contrast when a synthetic AP C-terminal 26-mer peptide
was added to plasma there was a twofold increase in the
rate of fibrinolysis probably as a result of a direct inter-
action with plasminogen causing conformational change
and accelerated activation to plasmin [33]. This is con-
sistent with the observation that it is clot bound AP
which modulates fibrinolysis and that interaction of free
plasmin and antiplasmin is probably more important in
preventing a systemic lytic state.
Whether antiplasmin will be useful as a therapeutic
target remains to be seen. There is, however, unmet
clinical need in the area of fibrinolysis. An agent that
increased the efficiency of endogenous fibrinolysis
would be useful to assist in the clearance of venous
thrombi. Furthermore, calf vein thrombosis is a com-
mon complication of surgery which often becomes
clinically manifest upon extension into proximal veins.
Antiplasmin inhibitors which biased in favour of clot
lysis may well be useful either post-operatively or in
long-term secondary prophylaxis for patients with
thrombotic disorders. Other situations in which this
approach may be useful is in diseases where fibrin
deposition is a key component of disease progression
such as glomerulonephritis.
Despite the fact that arterial and venous thrombosis
are common problems, responsible for major morbid-
ity and mortality, there are relatively few antithrom-

botic drugs available to the clinician. So far the
pharmaceutical industry has mainly focused on the
development of plasminogen activators for use in acute
arterial occlusion. Attention is beginning to shift to
PAI-1 as a possible target in view of its role in athero-
thrombotic disease. There is however, ample scope for
the investigation of therapeutic approaches using new
targets like antiplasmin to broaden the range of agents
available to clinicians and their patients.
References
1 Bateman JB, Pettit TH, Isenberg SJ & Simons KB
(1986) Ligneous conjunctivitis: an autosomal recessive
disorder. J Pediatr Ophthalmol Strabismus 23, 137–140.
2 Schuster V, Seidenspinner S, Zeitler P, Escher C, Pleyer
U, Bernauer W et al. (1999) Compound-heterozygous
mutations in the plasminogen gene predispose to the
development of ligneous conjunctivitis. Blood 93, 3457–
3466.
3 Carmeliet P & Collen D (1997) Molecular analysis of
blood vessel formation and disease. Am J Physiol 273,
H2091–H2104.
4 Favier R, Aoki N & de Moerloose P (2001) Congenital
alpha (2) -plasmin inhibitor deficiencies: a review. Br J
Haematol 114, 4–10.
5 Prandoni P, Lensing AW, Prins MH, Bernardi E,
Marchiori A, Bagatella P et al. (2002) Residual venous
thrombosis as a predictive factor of recurrent venous
thromboembolism. Ann Intern Med 137, 955–960.
6 Wiman B & Collen D (1977) Purification and character-
ization of human antiplasmin, the fast-acting plasmin

inhibitor in plasma. Eur J Biochem 78, 19–26.
7 Lijnen HR (2001) Gene targeting in hemostasis.
Alpha2-antiplasmin. Front Biosci 6, D239–D247.
8 Irving JA, Pike RN, Lesk AM & Whisstock JC (2000)
Phylogeny of the serpin superfamily: implications of
patterns of amino acid conservation for structure and
function [In Process Citation]. Genome Res 10, 1845–
1864.
9 Hirosawa S, Nakamura Y, Miura O, Sumi Y & Aoki N
(1988) Organization of the human alpha 2-plasmin inhi-
bitor gene. Proc Natl Acad Sci USA 85, 6836–6840.
10 Rijken DC, Groeneveld E, Kluft C & Nieuwenhuis HK
(1988) Alpha 2-antiplasmin Enschede is not an inhibi-
tor, but a substrate, of plasmin. Biochem J 255, 609–
615.
11 Kluft C, Nieuwenhuis HK, Rijken DC, Groeneveld E,
Wijngaards G, van Berkel W, Dooijewaard G & Sixma JJ
(1987) alpha 2-Antiplasmin Enschede: dysfunctional
alpha 2-antiplasmin molecule associated with an auto-
somal recessive hemorrhagic disorder. J Clin Invest 80,
1391–1400.
12 Holmes WE, Lijnen HR, Nelles L, Kluft C, Nieuwenhuis
HK, Rijken DC & Collen D (1987) Alpha 2-antiplasmin
Enschede: alanine insertion and abolition of plasmin inhi-
bitory activity. Science 238, 209–211.
13 Zhou A, Carrell RW & Huntington JA (2001) The ser-
pin inhibitory mechanism is critically dependent on the
length of the reactive center loop. J Biol Chem 276,
27541–27547.
Antiplasmin – the forgotten serpin? P. B. Coughlin

4856 FEBS Journal 272 (2005) 4852–4857 ª 2005 FEBS
14 Koie K, Kamiya T, Ogata K & Takamatsu J (1978)
Alpha2-plasmin-inhibitor deficiency (Miyasato disease).
Lancet 2, 1334–1336.
15 Lijnen HR, Okada K, Matsuo O, Collen D &
Dewerchin M (1999) Alpha2-antiplasmin gene deficiency
in mice is associated with enhanced fibrinolytic potential
without overt bleeding. Blood 93, 2274–2281.
16 Matsuno H, Okada K, Ueshima S, Matsuo O &
Kozawa O (2003) Alpha2-antiplasmin plays a significant
role in acute pulmonary embolism. J Thromb Haemost 1,
1734–1739.
17 Koyama T, Koike Y, Toyota S, Miyagi F, Suzuki N &
Aoki N (1994) Different NH2-terminal form with 12
additional residues of alpha 2-plasmin inhibitor from
human plasma and culture media of Hep G2 cells.
Biochem Biophys Res Commun 200, 417–422.
18 Lee KN, Lee CS, Tae WC, Jackson KW, Christiansen VJ
& McKee PA (2000) Cross-linking of wild-type and
mutant alpha 2-antiplasmins to fibrin by activated factor
XIII and by a tissue transglutaminase. J Biol Chem 275,
37382–37389.
19 Sakata Y & Aoki N (1982) Significance of cross-link-
ing of alpha 2-plasmin inhibitor to fibrin in inhibition
of fibrinolysis and in hemostasis. J Clin Invest 69,
536–542.
20 Lee KN, Jackson KW, Christiansen VJ, Chung KH &
McKee PA (2004) A novel plasma proteinase potenti-
ates alpha2-antiplasmin inhibition of fibrin digestion.
Blood 103, 3783–3788.

21 Lijnen HR, Holmes WE, van Hoef B, Wiman B, Rodri-
guez H & Collen D (1987) Amino-acid sequence of
human alpha 2-antiplasmin. Eur J Biochem 166, 565–
574.
22 Christensen S, Valnickova Z, Thogersen IB, Olsen E &
Enghild JJ (1997) Assignment of a single disulphide
bridge in human alpha(2)-antiplasmin: Implications for
the structural and functional properties. Biochem J 323,
847–852.
23 Lobov S, Wilczynska M, Bergstrom F, Johansson LB &
Ny T (2004) Structural bases of the redox-dependent
conformational switch in the serpin PAI-2. J Mol Biol
344, 1359–1368.
24 Wilczynska M, Lobov S, Ohlsson PI & Ny T (2003)
A redox-sensitive loop regulates plasminogen activator
inhibitor type 2 (PAI-2) polymerization. EMBO J 22,
1753–1761.
25 Streatfeild-James RM, Williamson D, Pike RN, Tewks-
bury D, Carrell RW & Coughlin PB (1998) Angiotensi-
nogen cleavage by renin: importance of a structurally
constrained N-terminus. FEBS Lett 436, 267–270.
26 Wiman B, Boman L & Collen D (1978) On the kinetics
of the reaction between human antiplasmin and a low-
molecular-weight form of plasmin. Eur J Biochem 87,
143–146.
27 Frank PS, Douglas JT, Locher M, Llinas M & Schaller J
(2003) Structural ⁄ functional characterization of the alpha
2-plasmin inhibitor C-terminal peptide. Biochemistry 42,
1078–1085.
28 Kluft C, Los P, Jie AF, van Hinsbergh VW, Vellenga E,

Jespersen J & Henny CP (1986) The mutual relationship
between the two molecular forms of the major fibrinolysis
inhibitor alpha-2-antiplasmin in blood. Blood 67, 616–
622.
29 Sasaki T, Morita T & Iwanaga S (1986) Identification
of the plasminogen-binding site of human alpha 2-plas-
min inhibitor. J Biochem (Tokyo) 99, 1699–1705.
30 Lee KN, Tae WC, Jackson KW, Kwon SH & McKee PA
(1999) Characterization of wild-type and mutant
alpha2-antiplasmins: fibrinolysis enhancement by reactive
site mutant. Blood 94, 164–171.
31 Sakata Y, Eguchi Y, Mimuro J, Matsuda M & Sumi Y
(1989) Clot lysis induced by a monoclonal antibody
against alpha 2-plasmin inhibitor. Blood 74, 2692–2697.
32 Kimura S, Tamaki T & Aoki N (1985) Acceleration of
fibrinolysis by the N-terminal peptide of alpha 2-plas-
min inhibitor. Blood 66, 157–160.
33 Lee KN, Jackson KW & McKee PA (2002) Effect of a
synthetic carboxy-terminal peptide of alpha (2) -anti-
plasmin on urokinase-induced fibrinolysis. Thromb Res
105, 263–270.
P. B. Coughlin Antiplasmin – the forgotten serpin?
FEBS Journal 272 (2005) 4852–4857 ª 2005 FEBS 4857