Fig. 4

Gastric acid is involved in the processing of rAc-cathB-2. a The effects of pepsin, HCl and pepsin-HCl on the expression of Ac-cathB-2 gene were tested by qRT-PCR. No obvious effect on the mRNA amounts of Ac-cathB-2 gene was detected in comparison with the control (PBS). b Cleavage of rAc-cathB-2. Equal amounts of rAc-cathB-2 were incubated with PBS, pepsin-HCl and HCl for 0.5 h in the presence of 5 mM DTT. Lane 1, molecular weight markers; Lanes 2–4, different treatments as indicated; c Proteolytic activity of rAc-cathB-2 from all three groups above was assessed at 37 °C by degrading the fluorescent substrate Z-RR-AMC. A control of pepsin-HCl without rAc-cathB-2 was also incubated with Z-RR-AMC. The fluorescence of the released AMC was measured with excitation and emission wavelengths of 355 and 460 nm, respectively. The data are presented as relative activities of Ac-cathB-2 after background correction, and the average activity of the PBS-treated groups was taken as 1. Asterisk indicates P < 0.05