α2-Antiplasmin Enschede is not an inhibitor, but a substrate, of plasmin
article
α2-Antiplasmin Enschede is a variant of α2-antiplasmin which has lost its ability to inhibit plasmin irreversibly and which is associated with haemorrhagic disorder [Kluft et al. (1987) J. Clin. Invest. 80, 1391-1400]. The abnormal protein was purified from the plasma of a homozygous patient and subjected to one-dimensional peptide mapping using papain for digestion. A slightly abnormally migrating polypeptide (M(r) 17,000) was found which represented the C-terminal part of the molecule (the N-terminus of the polypeptide corresponded to Gly-338 in normal α2-antiplasmin) and which contained the reactive centre. The interaction of plasmin with α2-antiplasmin Enschede was studied by adding plasmin to plasma of the homozygous patient. SDS/polyacrylamide-gel electrophoresis and immunoblotting showed that no complex persisted, but that the abnormal α2-antiplasmin was cleaved into two fragments of M(r) 56,000 and 14,000 respectively. The latter fragment co-migrated with the post-complex peptide, which is cleaved from normal α2-antiplasmin during complex-formation with plasmin. In a purified system, catalytic amounts of plasmin rapidly cleaved α2-antiplasmin Enschede into the aforementioned fragments. In kinetic studies α2-antiplasmin Enschede reversibly and temporarily inhibited the plasmin-catalysed hydrolysis of D-valyl-L-leucyl-L-lysine p-nitroanilide ('S-2251') as a competitive inhibitor (K(i,app. 35 nM). It was concluded that α2-antiplasmin Enschede apparently forms a normal complex with plasmin. The complex is, however, not stable, but disintegrates rapidly to a cleaved form of α2-antiplasmin Enschede and active plasmin. The abnormal protein thus behaves like a substrate, instead of an inhibitor, of plasmin. Chemicals/CAS: antiplasmin, 9049-68-7; plasmin, 9001-90-5, 9004-09-5; alpha(2)-antiplasmin Enschede; Antiplasmin; Oligopeptides; Plasmin, EC 3.4.21.7; valyl-leucyl-lysine 4-nitroanilide, 63589-93-5
Topics
alpha 2 antiplasminantiplasminplasminautosomal recessive disorderbleeding disorderheredityhuman cellAmino Acid SequenceAntiplasminElectrophoresis, Polyacrylamide GelHemorrhagic DisordersHumanHydrolysisImmunoblottingKineticsMolecular Sequence DataOligopeptidesPeptide MappingPlasminSupport, Non-U.S. Gov't
TNO Identifier
230529
ISSN
0264-6021
Source
Biochemical Journal, 255(2), pp. 609-615.
Pages
609-615
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