3.4.21.101 37 - pH 3.5-5.3, 20 h, stable 137235 3.4.21.101 37 - pH 4.0-5.5, 15 h, stable 137232 3.4.21.101 45 - 15 min, stable below 137232 3.4.21.101 50 - pH 4.8, 15 min, stable below 137235 3.4.21.101 60 - pH 4.8, 15 min, complete loss of activity 137235 3.4.21.101 65 - 15 min, complete loss of activity 137232