S. Finney et al., TRIDEGIN, A NEW PEPTIDIC INHIBITOR OF FACTOR XIIIA, FROM THE BLOODSUCKING LEECH HAEMENTERIA-GHILIANII, Biochemical journal, 324, 1997, pp. 797-805
1. Crude salivary gland extract of the giant Amazon leech, Haementeria
ghilianii, contains an inhibitor of plasma factor XIIIa. 2. The inhib
itory agent was purified to homogeneity by anion-exchange, cation-exch
ange, gel-filtration and reverse-phase chromatography to yield a singl
e band on SDS/PAGE with an apparent molecular mass of 7.3 kDa. It has
been named tridegin. 3. Micro-sequencing of proteolytic fragments show
ed tridegin to be a peptide of 66 amino acids. The sequence is unique
with little similarity to other leech-derived proteins. 4. Inhibition
of plasma factor XIIIa activity was confirmed by four independent meth
ods: tridegin increased the solubility of fibrin clots ia-urea, inhibi
ted ammonia produced from the incorporation of ethylamine into casein,
inhibited the incorporation of 5'-(biotinamido)pentylamine into casei
n and prevented gamma- dimer formation in clotting fibrinogen. 5. The
IC50 of tridegin (approx. 9.2 nM) is very close to the concentration o
f factor XIIIa used in the assay and in fact depends on its concentrat
ion. This is the most potent inhibitor of factor XIIIa yet described.
6. Tridegin also inhibits platelet factor XIIIa (factor XIIIAa) with a
similar potency to that of the plasma enzyme. 7. Tridegin also inhibi
ts tissue transglutaminase but with lower potency and independently of
the enzyme concentration. 8. Tridegin appears to be specific for tran
sglutaminases, since it has no effect on the coagulation times of huma
n plasma, on thrombin or factor Xa. Moreover it has no effect on other
thiol-containing enzymes and has no ability to digest fibrinogen or c
leave the isopeptide substrate, L-gamma-glutamyl-4-nitroanilide.