Figure 4.

Characterization of WT, Y75C, and I99C β-tryptases. A, size-exclusion chromatography of tetrameric WT, Y75C, and I99C β-tryptases was carried out as in Fig. 2 on an S200GL column in SEC buffer; the dimeric zymogens of Y75C and I99C β-tryptases were activated and then run on SEC. Elution volumes for the tetrameric peaks were 13.0 ml, which were pooled separately. B, SDS-PAGE of pooled tetrameric WT, Y75C, and I99C β-tryptases under nonreducing (NR) and reducing (R) conditions. C, enzymatic activity of tetrameric WT, Y75C, and I99C β-tryptases at 1 nm concentration using S-2288 as a substrate. Data were collected in triplicate and fit to the Michaelis-Menten equation; errors are shown as S.D.