Proteinase inhibitors association constants

To look for possible relations of thermal stabilization, measured as increase in Td, to other parameters of the proteinase—inhibitor interaction, we plotted increases in Td of the proteinases resulting from their association with the inhibitors as a function of the logarithms of the equilibrium association constants (log Kai or). Published values of Kgssoc vary somewhat (see Zahniey, 1980, W references to values used), and these values were not determined under the same conditions as used for the DSC experiments. Accordingly, ranges of log Kgssoc vere used in Figure 8. Values fell within a narrow... 

Figure 8. Stabilization of proteinases (aT ) on association with their protein inhibitors as a function of the logarithms of the equilibrium association constants (log K ssoc). Horizontal bar lines are used to indicate the range of log Kassoc values. Key to inhibitors (inside Figure, at lower right) OM, chicken ovomucoid for other abbreviations, see Table II. Key to proteinases BT, bovine p-trypsin PT, porcine 6-trypsin ...

Like SLPI, elafin is a very potent inhibitor of NE. Elafin interacts with elastase in a reversible manner and retains its inhibitory capacity upon dissociation of the complex. Kinetic data have shown that the association rate constant for the formation of an elafin-elastase complex is pH dependent [84]. Una is probably due to the bask properties of the inhibitor and enzyme. Elafin also inhibits proteinase 3 but has no effect on cathepsin G, trypsin, or chymotrypsin. This is inloestiitg in view of the fact that SLPI inhibits cathepsin G but la relatively ineffective against proteinase 3. 

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