The carbohydrate moiety of factor V modulates inactivation by activated
protein C
JA Fernandez, TM Hackeng, K Kojima and JH Griffin
Department of Molecular and Experimental Medicine, The Scripps Research
Institute, La Jolla, CA 92037, USA.
An important risk factor for thrombosis is the polymorphism R506Q in factor
V that causes resistance of factor Va to proteolytic inactivation by
activated protein C (APC). To study the potential influence of the
carbohydrate moieties of factor Va on its inactivation by APC, factor V was
subjected to mild deglycosylation (neuraminidase plus N-glycanase) under
nondenaturing conditions. The APC resistance ratio values (ratio of
activated partial thromboplastin time [APTT] clotting times with and
without APC) of the treated factor V were increased (2.4 to 3.4) as
measured in APTT assays. O-glycanase treatment of factor V did not change
the APC resistance ratio. The procoagulant activity of factor V as well as
its activation by thrombin was not affected by mild deglycosylation.
Treatment of factor V with neuraminidase and N-glycanase mainly altered the
electrophoretic mobility of the factor Va heavy chain, whereas treatment
with O- glycanase changed the mobility of the connecting region. This
suggests that the removal of the N-linked carbohydrates from the heavy
chain of factor Va, which is the substrate for APC, is responsible for the
increase in susceptibility to inactivation by APC. Thus, variability in
carbohydrate could account for some of the known variability in APC
resistance ratios, including the presence of borderline or low APC
resistance ratios among patients who lack the R506Q mutation.
Volume 89,
Issue 12,
pp. 4348-4354,
06/15/1997
Copyright © 1997 by The American Society of Hematology
