Measurement of the kinetic parameters mediating protease-serpin inhibition.

Serine protease inhibition by proteins of the serpin family is a unique and complex process involving physical, chemical, and conformational changes. After encounter with the reactive site of inhibitor, the protease is conformationally trapped as a covalent complex resembling the acyl-protease intermediate of catalysis. The stability of the trap is not permanent and may vary for different proteases.

Mast cell chymase modifies cell-matrix interactions and inhibits mitogen-induced proliferation of human airway smooth muscle cells.

The hallmarks of chronic, severe asthma include prominent airway inflammation and airway smooth muscle (ASM) hypertrophy and hyperplasia. One of the factors that contribute to the injury and repair process within the airway is activation of proteases and turnover of extracellular matrix components. Mast cells, which are present in increased numbers in the asthmatic airway, are a rich source of the neutral protease chymase, which can degrade several basement membrane components.

The effects of reactive site location on the inhibitory properties of the serpin alpha(1)-antichymotrypsin.

The large size of the serpin reactive site loop (RSL) suggests that the role of the RSL in protease inhibition is more complex than that of presenting the reactive site (P1 residue) to the protease. This study examines the effect on inhibition of relocating the reactive site (Leu-358) of the serpin alpha(1)-antichymotrypsin either one residue closer (P2) or further (P1') from the base of the RSL (Glu-342). alpha(1)-Antichymotrypsin variants were produced by mutation within the P4-P2' region; the sequence ITLLSA was changed to ITLSSA to relocate the reactive site to P2 (Leu-357) and to ITITLS to relocate it to P1' (Leu-359).

Heterogeneity in serpin-protease complexes as demonstrated by differences in the mechanism of complex breakdown.

Serpins trap their target proteases in the form of an acyl-enzyme complex. The trap is kinetic, however, and thus serpin-protease complexes ultimately break down, releasing a cleaved inactive serpin and an active protease. The rates of this deacylation process vary greatly depending on the serpin-protease pair with half-lives ranging from minutes to months.