The rate of kallikrein cleavage of CHO cell–expressed HK light chain. (A) Western blot detects a specific 40-kDa band of the recombinant (His)₆–HK4-6 in all 3 strains and shows the disappearance of the (His)₆ tag band as it is cleaved by kallikrein. (B) Quantitative densitometric analysis of the (His)₆–HK4-6. The rate of cleavage as a function of time was analyzed. ○ indicates Lewis; □, Fischer; and ▿, Buffalo. Mean ± SEM, n = 3. The Lewis recombinant (His)₆-tagged HK cleavage was significantly faster than observed in the Fischer or Buffalo rat recombinants.