Interaction of bovine factor XIIa with an inhibitor from bovine plasma

Features of a newly cloned pig C1 esterase inhibitor

The pig cDNA encoding C1 esterase inhibitor (C1-INH) was isolated and the homology of the sequence was compared with that from other animals. The structure of pig C1-INH contains a two disulfide bridge pattern identical to the human C1-INH. In the amino acid sequence of the first Cys-91 to the C-terminal end, the pigC1-INH has a 76.2% homology with the human protein, and the sequence of the reactive site is close to the human. A surface-bound form of pig and human C1-INH, pC1-INH-PI and hC1-INH, respectively, were next constructed. Stable Chinese hamster ovarian tumor (CHO) cell lines and pig endothelial cell (PEC) lines expressing these C1-INH-PI were prepared by transfection. The basic function and the species specificity of pCI-INH were then investigated using these transfectants. pC1-INH and hC1-INH have almost the same suppressive effect on pig, human, dog and rabbit sera in complement-dependent cell lysis, indicating little species specificity.

Inhibition of prekallikrein activation in human plasma by components of bovine plasma

Contact of plasma with a negatively charged surface activates prekallikrein and factor XII reciprocally. Activation of prekallikrein by several activators was impaired in bovine plasma when compared to that in human plasma. The activated partial thromboplastin time of bovine plasma, induced by several activators, was significantly longer than that of human plasma. Cleavage of [125I]factor XII was optimum at 10 min in human plasma but took up to 60 min in bovine plasma. Addition of bovine plasma to human plasma caused significant inhibition of dextran sulfate-induced prekallikrein activation, indicating that the impaired rate of contact activation in bovine plasma is due to the presence of inhibitors. The inhibitory effect was greater at lower concentrations of dextran sulfate but could not be abolished by increasing the concentration. The inhibitory activity eluted in two peaks at low and medium salt concentrations on carboxymethyl ion-exchange chromatography of bovine plasma.

Prekallikrein activation in human, bovine, and rabbit plasmas: presence of an inhibitor in bovine plasma

Contact of human plasma with a negatively charged surface such as dextran sulfate activates prekallikrein to kallikrein, which releases the vasoactive peptide bradykinin from high-molecular-weight kininogen. The dextran sulfate-induced activation of prekallikrein at 0 degree C (assayed by its amidolytic activity on the chromogenic substate S-2302) could not be observed in either bovine or rabbit plasmas when compared to human plasma. Neither bovine nor rabbit plasma inhibited the amidolytic activity of contact-activated human plasma at 0 degrees C. The activation of prekallikrein in human plasma was significantly inhibited by the addition of bovine plasma but not by rabbit plasma. Bovine plasma (0.025 units, 1 unit = 1 ml of plasma) caused 68.8% inhibition of prekallikrein activation. Eighty percent of the inhibitory property of bovine plasma was present in the greater than 30,000-molecular-weight fraction. These results indicate the presence of an inhibitor(s) of prekallikrein activation in bovine plasma.