Kinetics of interaction of trypsin with an anionic inhibitor of trypsin BWI-1a from buckwheat seeds.

The kinetics of binding of bovine trypsin to a proteinaceous inhibitor of trypsin from buckwheat seeds (BWI-1a) has been studied. The association rate constant (k(ass)) was 2.2 x 10(6) M-1 x sec-1 and the dissociation rate constant (k(off)) of the enzyme--inhibitor complex was 3.5 x 10(-3) sec-1; the inhibition constant Ki was 1.5 nM. The inhibitor BWI-1a is of the slow, tightly binding type. The mechanism of the inhibition of bovine trypsin by the trypsin inhibitor BWI-1a was studied. The mechanism of inhibition was found to involve two steps according to the kinetic data.

Human leukocyte elastase inhibition by Bowman-Birk soybean inhibitor. Discrimination of the inhibition mechanisms.

The reaction between human leukocyte elastase and soybean Bowman-Birk inhibitor has been studied. The inhibition was found to be due to slow tight binding of the inhibitor. The interaction of BBI with HLE was shown to involve two steps: the rapid formation of an initial EI complex, with a Ki of 28 nM, followed by a slow equilibrium conversion to a tighter-binding EI* complex with a final Ki* of 2.3 nM. At pH 7.5 and 25 degrees C, k(on) was 3.5 x 10(4) M(-1) s(-1) and k(off) was 1.0 x 10(-4) s(-1).

[Inhibition of exogenous serine proteinases by a trypsin inhibitor from the buckwheat IT-1 seeds]. / Ingibirovanie ékzogennykh serinovykh proteinaz ingibitorom tripsina iz semian grechikhi IT-1.

The possibility of inhibition of exogenous trypsin- and chymotrypsin-like proteinases by a proteinase inhibitor from buckwheat (IT-1) seeds has been studied. The inhibition constants for bovine trypsin and alpha-chymotrypsin and human granulocyte cathepsin G by IT-1 are equal to 1.1, 67 and 200 nm, respectively. The specificity of IT-1 with regard to its primary sequence adjacent to the active center and to its homology with inhibitors pertaining to the potato inhibitor I family has been carried out. It is concluded that by virtue of the basic nature of the P1 (Arg) residue in the active center IT-1 is not capable to bind human granulocyte elastase.

[The classical Bowman-Birk soy inhibitor is an effective inhibitor of human granulocyte alpha-chymotrypsin and cathepsin G]. / Klassicheskii soevyi ingibitor tipa Baumana-Birk--éffektivnyi ingibitoralpha-khimotripsina i katepsina G granulotsitov cheloveka.

A kinetic study of the interaction of the classical Bowman-Birk type soybean inhibitor (BBI 2-IV) with human granulocyte alpha-chymotrypsin and cathepsin G has been carried out. The K(a) values for the inhibitor-proteinase systems--alpha-chymotrypsin and cathepsin G (2.0 x 10(5) and 6.4 x 10(6) M-1 s-1, respectively) have been established.