Guava (Psidium guajava L.) leaf protease activity enriched by controlled-stress and putrescine application

Abstract

Plant-derived proteases are widely used in the food and pharmaceutical industries. Some enzyme operations require enzyme activity and stability at high temperatures or extremes of pH. We sought a simple, low-priced, and nature-friendly method to improve protease activity and stability. Guava was chosen as the plant protease source. Plants were treated with saline water (0, 5 and 10 dS /m) and foliar application of putrescine (0, 250 and 500 ppm). Leaf protease activity was evaluated at a range of pH (2–8) and temperature (30–90 °C). Salt, putrescine and their combination significantly influenced protease activity. Putrescine application (250 ppm) increased enzyme activity at high temperatures and acidic pH in leaf extracts. For plants irrigated with high saline, 500 ppm putrescine treatment increased both the low pH and high pH protease activities. The existence of two pH optima of guava leaf protease suggests that at least two major proteases are present in the guava leaf extract.