The Conversion of Prethrombin to Thrombin

Abstract

SummaryPurified prethrombin was converted to thrombin in an activating system consisting of purified autoprothrombin C, purified Ac-globulin, lipid and calcium chloride. With the concentration of calcium and pH fixed, the effect of varying the other 3 pro-coagulants was studied.Conditions influencing the conversion of prethrombin to thrombin were determined. Autoprothrombin C is the enzyme, but with it alone activation was very slow. Best results were obtained with the simultaneous presence of autoprothrombin C, Ac-globulin and lipid. Reducing any one of the three toward zero concentration decreased the rate and yield of thrombin generation. In association with rapid thrombin generation Ac-globulin and autoprothrombin C were represented in approximately a 1:1 molar ratio. In that combination of Ac-globulin and autoprothrombin C the Michaelis constant for autoprothrombin C with prethrombin as a substrate was 3.14 × 10-6M.

XIV. Prothrombinase Complex

“…Note apparent stoichiometric nature of thrombin yield and its low yield from a possible 1300 U. Under same conditions, yield from prothrombin would be 100% (assembled from data of Baker and Seegers 1967). varied. Control 1 without Factor V, control 2 without lipid, con trol 3 without Factor V or lipid.…”

“…Information on both was essential. We set up the following experimental pro jections with purified reagents: (Baker and Seegers 1967;Seegers, McCoy and Marciniak 1968;Seegers 1968) it was concluded that any one of the variables could be re duced in concentration and be associated with a re duction in thrombin yield (Fig. 1).…”

V. Amino Acid Sequence of Bovine and Human Prothrombin

“…Earlier, Malhotra and Carter (1971) had isolated atypical prothrombin from the plasma of dicumarolized steers. Even before that there appeared a de scription of the characteristics of thrombin genera tion from purified prethrombin 1 in the presence of purified Factor Xa, purified Factor V, phospholipid and calcium ions (Baker and Seegers 1967). At that time it was known only that prethrombin 1 had a smaller molecular weight than prothrombin, but was larger than thrombin.…”

“…In the generation of thrombin from prethrombin 1 (Baker and Seegers 1967), any one of the compo nents-namely, prethrombin 1, Factor V, Factor Xa, phospholipid or calcium ions -could be re duced below optimum concentration with a resulting diminution in thrombin yield. This is simi lar to the facts observed with prothrombin as sub strate.…”

VII. Ac-Globulin (Factor V)

“…The first time it was possible to obtain quantitative data on these interrelationships we used prethrombin 1, crude cephalin, and Ac-globulin concentrate free of other coagulation factors. Prethrombin 1, and Factor Xa were purified single component systems (Baker and Seegers 1967;Seegers 1968). We made the following combinations: ‡This specimen of plasma was obtained after 300 ml of whole blood had been infused.…”