SDS-PAGE of protease–peptide reaction mixtures. Each substrate of residues 168–266, 189–256, 189–266 or 168–256 of PH1511p (1 µg) was degraded by the 1510-N protease (0.25 µg) with incubation at 353 K in a buffer containing 50 mM MES-NaOH (pH 6.0). Protease, substrate and degraded products after 0, 5, 10, 20, 35 and 50 min reaction were observed. Asterisks indicate substrate bands. Two degraded products were definitely identified as indicated by residue numbers. Putative acyl-enzyme intermediates were also detected as indicated. Lane M indicates molecular markers.