One katal (kat) is the amount of enzyme that converts one mole of substrate per second. Activated enzymes from Chromogenix such as FXa and thrombin are measured in nkat. 1 nkat = 1 x 10-9 mol of product released per second. The conversion is as follows:
FXa has a MW approximately 44,000.
The specific activity for FXa is 1.9 nkat/mg, as determined with chromogenic substrate S-2222.
This gives that 71 nkat corresponds to 37.4 mg FXa (=37.4 x10-6 g FXa)
This corresponds to 8.5 x 10-10 mol = 0.85nmol.
The concentration in mol/l and g/l will depend on the dilution volume you choose.
Note: 1 IU corresponds to 20 nkats, which means 71 nkatS-2222 = 3.55 IU.