^(13)C NMR studies of the binding of soybean trypsin inhibitor to trypsin

Abstract

NMR studies of the complex between trypsin and soybean trypsin inhibitor with 1-^(13)C-arginine and modified inhibitor with 1-^(13)C-lysine show that these complexes involve almost exclusively non-covalent binding of the inhibitor to the enzyme for trypsin/^(13)C-Lys-inhibitor at pH 6.5 and 8.1 and for trypsin/^(13)C-Arg-inhibitor at pH 5.0. At pH 7.1 for trypsin/^(13)C-Arg-inhibitor both non-covalent and acyl enzyme forms are observed. Under no conditions did we observe evidence for a tetrahedral adduct between enzyme and inhibitor.

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