ISSN:
0952-3499
Keywords:
Chemistry
;
Biochemistry and Biotechnology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Medicine
Notes:
The effect of pH and temperature on the apparent association equilibrium constant (Ka) for the binding of the soybean Bowman-Birk proteinase inhibitor (BBI) and of its chymotrypsin and trypsin inhibiting fragments (F-C(p), F-T(p) and F-T(t), respectively) to bovine α-chymotrypsin (α-chymotrypsin) and bovine β-trypsin (β-trypsin) has been investigated. On the basis of Ka values, the proteinase inhibitor affinity can be arranged as follows: β-chymotrypsin: BBI ≈ β-trypsin:BBI ≈ β-trypsin:F-T(t) ≈ β-trypsin:F-T(p) ≫ α-chymotrypsin:F-C(p), F-C(p), F-T(p) and F-T(t) do not inhibit β-trypsin and α-chymotrypsin action, respectively. On lowering the pH from 9.5 to 4.5, values of Ka for BBI, F-C(p), F-T(p) and/or F-T(t) binding to α-chymotrypsin and β-trypsin decrease, thus reflecting the acid-pK shift of the invariant His57 catalytic residue from 7.0, in the free enzymes, to 5.2, in the proteinase:inhibitor complexes. Considering the known molecular models, the observed binding behaviour of BBI, F-C(p), F-T(p) and F-T(t) was related to the inferred stereochemistry of the proteinase:inhibitor contact regions.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jmr.300030504
