The kinetics of trypsinogen activat

The kinetics of trypsinogen activation were analyzed under two conditions. At pH 5.6, interference from the autoactivation of trypsinogen is minimal, although enteropeptidase has reduced activity (23, 24). Under these conditions, BEK and HLBEK
had similar Km and kcat values, which are comparable to those reported previously for BEK: Km 5 17 mM and kcat 5 6.3 s21 (7) and Km 5 7 mM and kcat 5 1.48 s21 (6). In contrast, L-BEK cleaved trypsinogen relatively slowly; the Km was increased 24-fold, and the kcat was reduced 20–40-fold relative to HL-BEK and BEK (Table I). Qualitatively similar results were obtained at pH 8.4, which is optimal for enteropeptidase. Under these conditions, the autoactivation of trypsinogen can be significant, but interference from this cause was prevented by inclusion of ovomucoid to inactivate the trypsin product (21). The Km for trypsinogen activation by L-BEK was increased 18-fold, and the kcat was decreased 2.5–3-fold.