FIGURE 6.

MALDI-TOF analysis of peptides generated by cathepsin L from recombinant proheparanase. Recombinant proheparanase was incubated (1 μg) with human cathepsin L (0.5 μg/ml) and subjected to MALDI-TOF analysis (A and B). Thirteen masses of peptides (P1–P13) corresponding to sequences with calculated masses similar to the measured masses (MALDI-TOF) ±20 daltons (see “Materials and Methods”) were detected. A, P1 (8244.29 daltons) corresponds to the exact size of the 8-kDa subunit (³⁶QD¹VV to Glu¹⁰⁹). P2, P3, P4, and P5 are elongated forms of the 8-kDa subunit plus ¹¹⁰STF¹¹², ¹¹⁰STFE¹¹³, ¹¹⁰STFEE¹¹⁴, and ¹¹⁰STFERSY¹¹⁷, respectively. B, P1, P4, and P5 were described in A. Peptides P6–P13 are all derived from the linker segment (see Fig. 7).