Fig. 2.

Inhibition of NE or proteinase 3 (PR3) activities by serum from various A1AT genotypes. Inhibition of NE (A) or PR3 (B) activity by PiMM, PiFZ, PiIZ, and PiZZ sera using N-Methoxysuccinyl-Ala-Ala-Pro-Val p-nitroanilide (MSaapvN) rather than SlaaapN as the substrate. Initially, neutrophil serine proteinase (NSP) activity decreases linearly as the ratio of A1AT:proteinase approaches 1:1, indicating that NSP inhibition largely reflects the inhibitory capacity of A1AT in serum. The residual NSP activity observed when serum A1AT is in a molar excess reflects partitioning of the enzyme to A2M, and this phenomenon is greater in the presence of mutant variants of A1AT. The SE is small and falls within the symbol.