authors of the herein invention purified a prothrombin activator serine protease of 69 kda the preliminary results have shown that the lopap activating capacity is independent of the prothrombinase complex however the ca 2 ions provoke an increase of this activity the lopap purifying process included the use of organic solvents causing a visible activity loss up to about 50 when using 30 of acetonitrile and 80 when using 50 of acetonitrile chart 1 therefore it is quite difficult to calculate the protein specific activity less radical purifying methods were not so efficient and currently the production of recombinant lopap is being performed lopap was characterized as being a serine protease activated through ca 2 ions and it is structurally different from other prothrombin activators described in literature the n terminal segment showed 45 6 of identity when compared to the n terminal portion of the purified insecticyanin of the manduca sexta hemolymph fragments i ii iii and iv showed respectively 36 4 37 5 42 9 and 55 5 of identity with the internal fragments sequence of the same protein g 86 q 97 d 124 e 148 i 160 y 177 the homogeneity of purified lopap was confirmed through only one n terminal residue the quenched fluorescence substrate was programmed for containing the thrombin bound arg 284 thr 285 flanked by the sequence tyr 277 ser 288 lopap cleaved this substrate in the peptidic bound corresponding to prothrombin cleaved by thrombin it was demonstrated by the herein invention that lopap is not able to activate the factor x and differently than lopap the activator of the factor x will require to be.