Skip to main content
Figure 6 | Respiratory Research

Figure 6

From: SP-A binds alpha1-antitrypsin in vitro and reduces the association rate constant for neutrophil elastase

Figure 6

Hypothetical mechanism of SP-A interference with α 1 -AT (simplification). A: interaction of α1-AT (I) with HNE (E). After an initial non-covalent Michaelis-like complex (EI), the interaction progresses through a tetrahedral intermediate (EI ♠), forming a covalent acyl-enzyme intermediate (EI ♥). The substrate pathway results in free HNE and cleaved α1-AT (I*); the inhibitory pathway results in a, about 100%, kinetically trapped loop-inserted covalent complex (E-I*). B: the SP-A (here shown as a trimer) interacts with α1-AT. In the presence of HNE, the formation of a covalent complex E-I* almost precluded (about 4%), and the reaction progresses through the substrate pathway towards free E and I* (cleaved α1-AT) – SP-A (96%). SI = stoichiometry of inhibition

Back to article page