R-VKORC1 expression in factor IX BHK cells increases the extent of factor IX carboxylation but is limited by saturation of another carboxylation component or by a shift in the rate-limiting step.

ABSTRACT: Carboxylation of vitamin K-dependent (VKD) proteins is required for their activity and depends on reduced vitamin K generated by vitamin K oxidoreductase (VKOR) and a redox protein that regenerates VKOR activity. VKD protein carboxylation is inefficient in mammalian cells, and to understand why carboxylation becomes saturated, we developed an approach that directly measures the extent of intracellular VKD protein carboxylation. Analysis of factor IX (fIX)-expressing BHK cells indicated that slow egress of fIX from the endoplasmic reticulum and preferential secretion of the carboxylated form contribute to secreted fIX being more fully carboxylated. The analysis also revealed the first reported in vivo VKD protein turnover, which was 14-fold faster than that which occurs in vitro, suggesting

SUBMITTER: Hallgren KW 

PROVIDER: S-EPMC2512261 | biostudies-literature | 2006 May

REPOSITORIES: biostudies-literature