Zinc ions bind to and inhibit activated protein C
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Zinc ions bind to and inhibit activated protein C. / Zhu, Tianqing; Ubhayasekera, Wimal; Nickolaus, Noëlle; Sun, Wei; Tingsborg, Susanne; Mowbray, Sherry L; Schedin-Weiss, Sophia.
I: Thrombosis and Haemostasis, Bind 104, Nr. 3, 01.09.2010, s. 544-553.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Zinc ions bind to and inhibit activated protein C
AU - Zhu, Tianqing
AU - Ubhayasekera, Wimal
AU - Nickolaus, Noëlle
AU - Sun, Wei
AU - Tingsborg, Susanne
AU - Mowbray, Sherry L
AU - Schedin-Weiss, Sophia
N1 - Keywords: activated protein C, serine protease, zinc, blood coagulation, enzyme inhibition
PY - 2010/9/1
Y1 - 2010/9/1
N2 - Zn2+ ions were found to efficiently inhibit activated protein C (APC), suggesting a potential regulatory function for such inhibition. APC activity assays employing a chromogenic peptide substrate demonstrated that the inhibition was reversible and the apparent K I was 13 +/- 2 microM. k cat was seven fold decreased whereas K M was unaffected in the presence of 10 microM Zn2+. The inhibitory effect of Zn2+ on APC activity was also observed when factor Va was used as a substrate in an assay coupled to a prothrombinase assay. The interaction of Zn2+ with APC was accompanied by a reversible approximately 40% decrease in tryptophan fluorescence, consistent with the ion inducing a conformational change in the protein. The apparent K D was 7.4 +/- 1.5 microM and thus correlated well with the apparent K I. In the presence of physiological Ca2+ concentration the K I and K D values were three to four fold enhanced, presumably due to the Ca2+-induced conformational change affecting the conformation of the Zn2+-binding site. The inhibition mechanism was non-competitive both in the absence and presence of Ca2+. Comparisons of sequences and structures suggested several possible sites for zinc binding. The magnitude of the apparent KI in relation to the blood and platelet concentrations of Zn2+ supports a physiological role for this ion in the regulation of anticoagulant activity of APC. These findings broaden the understanding of this versatile serine protease and enable the future development of potentially more efficient anticoagulant APC variants for treatments of thrombotic diseases.
AB - Zn2+ ions were found to efficiently inhibit activated protein C (APC), suggesting a potential regulatory function for such inhibition. APC activity assays employing a chromogenic peptide substrate demonstrated that the inhibition was reversible and the apparent K I was 13 +/- 2 microM. k cat was seven fold decreased whereas K M was unaffected in the presence of 10 microM Zn2+. The inhibitory effect of Zn2+ on APC activity was also observed when factor Va was used as a substrate in an assay coupled to a prothrombinase assay. The interaction of Zn2+ with APC was accompanied by a reversible approximately 40% decrease in tryptophan fluorescence, consistent with the ion inducing a conformational change in the protein. The apparent K D was 7.4 +/- 1.5 microM and thus correlated well with the apparent K I. In the presence of physiological Ca2+ concentration the K I and K D values were three to four fold enhanced, presumably due to the Ca2+-induced conformational change affecting the conformation of the Zn2+-binding site. The inhibition mechanism was non-competitive both in the absence and presence of Ca2+. Comparisons of sequences and structures suggested several possible sites for zinc binding. The magnitude of the apparent KI in relation to the blood and platelet concentrations of Zn2+ supports a physiological role for this ion in the regulation of anticoagulant activity of APC. These findings broaden the understanding of this versatile serine protease and enable the future development of potentially more efficient anticoagulant APC variants for treatments of thrombotic diseases.
KW - Former Faculty of Pharmaceutical Sciences
U2 - 10.1160/TH09-12-0862
DO - 10.1160/TH09-12-0862
M3 - Journal article
C2 - 20664913
VL - 104
SP - 544
EP - 553
JO - Thrombosis et diathesis haemorrhagica
JF - Thrombosis et diathesis haemorrhagica
SN - 0340-6245
IS - 3
ER -
ID: 33862891