Kinetics of the inhibition of free and elastin-bound human pancreatic elastase by alpha 1-proteinase inhibitor and alpha 2-macroglobulin |
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Authors: | P Laurent J G Bieth |
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Institution: | Laboratoire d'Enzymologie, INSERM Unité 237, Université Louis Pasteur de Strasbourg, Illkirch, France. |
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Abstract: | At pH 8.0 and 25 degrees C alpha 1-proteinase inhibitor and alpha 2-macroglobulin bind human pancreatic elastase with rate constants of 4.7.10(5) M-1.s-1 and 6.4.10(6) M-1.s-1, respectively. The corresponding delay times of elastase inhibition in plasma are 0.4 s and 0.2 s, respectively, indicating that both inhibitors may act as physiological antielastases. Elastin impairs the elastase inhibitory capacity of alpha 1-proteinase inhibitor and alpha 2-macroglobulin. In presence of human elastin, the former behaves like a slow-binding elastase inhibitor, with a rate constant of about 260 M-1.s-1. In contrast, alpha 2-macroglobulin is a fast-binding inhibitor of elastin-bound elastase, but only one of its two sites is functioning in presence of elastin. |
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