How is the rate of factor Xa affected by urea, guanidine hydrochloride and SDS?
The activity of factor Xa on the chromogenic substrate Bz-IEGR-pNA in the presence of these denaturants is as follows: Urea: In 0.25 M urea, factor Xa cleaves at about 33% its normal rate; at 0.5 M, 25% its normal rate, in 1 M urea, about 10% its normal rate, while in 2 M urea no cleavage is detected. Guanidine: In 0.25 M guanidine hydrochloride it cleaves at about 15% its normal rate, and in 0.5 M it cleaves at about 5% the normal rate. SDS: Factor Xa is unaffected by concentrations of SDS below 0.005%. At 0.01% it cleaves at about half its normal rate, and at 0.03% at about one-third normal. At 0.1% and above no cleavage is detected.
