Amino acid sequence and inhibitory activity of rhesus monkey tissue factor pathway inhibitor (TFPI): comparison with human TFPI.

Rhesus monkey cDNA for tissue factor pathway inhibitor (TFPI) was cloned by means of the reverse transcriptase-polymerase chain reaction, using liver mRNA, and its nucleotide sequence was determined by sequencing five independent clones. Monkey TFPI was found to have a signal peptide of 28 amino acid residues and to be a mature protein of 276 amino acid residues, in which three and seventeen amino acid residue substitutions compared to human TFPI were found, respectively. All the cysteine residues, three putative carbohydrate-linked asparagine residues, and the P1 amino acid residues of each of the three Kunitz inhibitor domains were conserved in the two species. Recombinant monkey TFPI (rTFPI) was isolated from the culture medium of transformed Chinese hamster ovary cells. Amino acid sequence analysis and immunoblotting analysis, using polyclonal and monoclonal antibodies, showed that the carboxyl-terminal basic part of Rhesus monkey rTFPI had been truncated. The inhibitory activity of monkey rTFPI was compared with that of human rTFPI without the carboxyl-terminal basic part. The prothrombin time of human plasma was slightly more prolonged by the addition of monkey rTFPI than by that of human rTFPI. However, no significant differences were found between the potencies of human and monkey rTFPI as to the inhibition of factor Xa and tissue factor-factor VIIa complex.