[Role of lysine binding sites in activation of plasminogen by streptokinase].
The function of lysine-binding sites in kringle domains K1-4 and K5 of plasminogen (Pg) during its activation by streptokinase (SK) was studied. Activation rates of Glu- and Lys-Pg exceed activation rate of mini- and micro-Pg 26 and 40 times, respectively. 6-Animohexanoic acid (6-AHA) in concentrations from 10(-5) to 10(-2) M inhibits activation of Glu-, Lys- and mini-Pg and does not impact the activation of micro-Pg. Complete inhibition of Lys-Pg activation occurs with presence of 10(-3) M 6-AHA while 90% inhibition of mini-Pg activation and 70% inhibition of Glu-Pg activation occur with 10(-2) M 6-AHA. Isolated kringles K1-3 and K4 of Pg inhibit activation of Glu-Pg by SK and concentrations [I]50 are 4.0 and 8.1 x 10(-6) M, respectively. Catalytic activity of Glu-Pg-SK, Lys-Pg-SK and Pm-SK complexes with respect to S 2251 is not inhibited by 6-AHA in concentrations from 10(-5) to 10(-2) M. Activation of substrate Pg by Pm-SK complex is also inhibited by 6-AHA in concentrations from 10(-5) to 10(-2) M; however, this effect of inhibition is significantly weaker than that with activation by SK. Cleavage of C-terminal Lys or chemical modification of NH2-groups of amino acid residues in SK molecule also results in the decrease of the Glu-Pg activation rate. Lysin-binding sites in K1-4 and K5 of Pg molecule are important at different steps of Pg activation process which includes formation of equimolar complex; structural reorganizations resulted in formation of active center in Pg; and binding of substrate Pg with Pg-SK complex. Lysin-binding sites in K1-4 of Pg are necessary for maintenance of high rate of Pg activation by SK.
Sokolovskaia
L I
LI
Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv. sokolovskaja@yahoo.com
Makogonenko
E M
EM
Grinenko
T V
TV
Cederholm-Williams
S A
SA
D015119:Aminocaproic Acid / Q000494:pharmacology; D000933:Antifibrinolytic Agents / Q000494:pharmacology; D001665:Binding Sites; D002384:Catalysis; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D005343:Fibrinolytic Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D018082:Kringles; D008239:Lysine / Q000378:metabolism*; D010958:Plasminogen / Q000737:chemistry / Q000378:metabolism*; D013300:Streptokinase / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D013379:Substrate Specificity
D000933:Antifibrinolytic Agents; D005343:Fibrinolytic Agents; D010958:Plasminogen; D013300:Streptokinase; D008239:Lysine; D015119:Aminocaproic Acid