Protein concentrations in plasma

Component

Molecular
Weight kDa

Plasma
Concentration
mg/l

Plasma
Concentration
μmol/l

Fibrinogen 330 3000 9
Prothrombin 72 150 2
Factor V 330 20 0.05
Factor VII 50 0.5 0.01
Factor VIII 330 0.1 0.0003
Factor IX 56 5 0.09
Factor X 59 8 0.13
Factor XI 160 5 0.03
Factor XII 80 30 0.4
Factor XIII 320 10 0.03
Protein C 62 4 0.06
Protein S 70 10 (free) 0.14
Protein Z 62 2 0.03
Prekallikrein 86 50 0.6
HMW kininogen 120 70 0.6
Fibronectin 450 300 0.7
Plasminogen 92 200 2
t-PA 60 0.005 0.0001
Urokinase 53 0.004 0.0001
Antithrombin 58 145 2.5
Heparin Cofactor II 66 80 1.2
Plasmin Inhibitor 63 60 1
Protein C Inhibitor 57 4 0.07
α2-Macroglobulin 725 2000 3

The activity of plasmin and plasminogen is expressed in CU. What is this, and what is the equivalent in nkat?

CU stands for Casein Units, and is a measure of the proteolytic activity on the substrate casein. For example, a plasminogen reagent when activated to plasmin with streptokinase can show an activity of 7.3 nkat (S-2251™) per CU. 1 mg of plasmin corresponds to 0.20 nkat (S-2251™), or to 0.024 CU.

What is the difference between Glu-plasminogen and Lys-plasminogen? How can the two forms be measured?

The native form of plasminogen in plasma has glutamic acid (Glu) at the N-terminal and is termed Glu-plasminogen. Other plasminogen forms generated by the catalytic cleavage of plasmin and containing mostly lysine (Lys) at the N-terminal position are termed Lys-Plasminogen. They can be measured using a chromogenic method based on the different rate of activation of the two forms by urokinase. See Scully MF, Kakkar VV. Measurement of Degraded Forms of Plasminogen in Human Plasma. Thromb Res (1980); 17: 347-352. Note that the Chromogenix plasminogen is at least 95% Glu-plasminogen.

Is the plasminogen reagent you sell Glu- or Lys- plasminogen?

We sell both forms, though most researchers want Glu-Plasminogen, which is a preparation of at least 95% Glu-plasminogen. See the product pages for detailed information about our plasminogen preparations.

What is the conversion factor for Antithrombin from IU to mg?

5 IU corresponds to 1 mg. Therefore a 25 IU vial corresponds to 5 mg AT. The molecular weight of AT is 58 kDa.

What is the 53 nkat vial of thrombin equivalent to in NIH units?

Based on an assay with S-2238™, for bovine thrombin, 1 NIH-U = 1.15 IU = 3.4 nkat. The DiaPharma bovine thrombin, 53 nkat (S-2238™) is equivalent to approximately 21 NIH-U or 25 IU.