Table 1.

Formation of vitamin K epoxide in the presence of proFIX18 and FLEEL

Omission(s)	γ-Carboxyglutamic acid, pmol per min per pmol of enzyme	Vitamin K 2,3-epoxide, pmol per min per pmol of enzyme
None	116.0	100.0
Minus vitamin K	0.05	ND
Minus FLAG-carboxylase	0.10	1.5
Minus propeptide, minus FLEEL	0.07	1.7
Minus propeptide	9.0	9.2
Minus FLEEL	0.28	3.4

Complete reaction mixture contains 64 μM proFIX18, 3.6 mM FLEEL, 222 μM vitamin K, and 1.24 pmol of FLAG-carboxylase in a reaction volume of 125 μl. NaH¹⁴CO₂ is added to 1.54 mM and is diluted 2.4-fold by endogenous CO₂ as determined by the method of Larson et al. (21). The pmol of γ-carboxyglutamic acid formed has been corrected to reflect this dilution of the C¹⁴ labeled CO₂. ND, not detectable.