Characterisation of the α1‐protease inhibitor system in Thoroughbred horse plasma by horizontal two‐dimensional (ISO‐DALT) electrophoresis. 2. Protease inhibition

Abstract

The protease inhibitory spectra of the 8 homozygous Thoroughbred Pi types against trypsin, elastase and chymotrypsin were determined. The .alpha.1-protease inhibitor proteins exhibit 3 classes of inhibitory specificity towards these enzymes. The Pi types F, I, N and U exhibit class I (trypsin, elastase and chymotrypsin) and class II (trypsin and elastase) types of inhibition and fit Juneja et al.''s classification of 2 separate genetic systems Pi 1 and Pi 2 based on differences in the inhibitory spectra against trypsin and chymotrypsin. The remaining 4 Pi types are exceptions to Juneja et al.''s classification. Types G, L, S1 and S2 possess class I but not class II proteins. A 3rd class of proteins (class III) which exclusively inhibit chymotrypsin was detected in all 8 protease inhibitor types. Type G is well represented by class III proteins because 2 of the 3 major proteins of the ISO-DALT pattern inhibit only chymotrypsin and is thus an exception to Juneja et al.''s classification.