Pineapple fruit bromelain affinity to different protein substrates

Optimal pH and temperature conditions for proteolytic activity of pineapple fruit bromelain were determined using five different substrates: azocasein and azoalbumin (pH 3-10 at 20-70 degrees C), casein and sodium caseinate (pH 2-10 at 20-70 degrees C), and haemoglobin (pH 2-6.5 at 30-60 degrees C). Fruit bromelain has shown optimum activity at pH 7.5 for azoalbumin and at 6.5 for azocasein, all at 55 degrees C. Fruit bromelain activity determined with casein and sodium caseinate has shown optimum activity at 59 degrees C. while the optimum pH was 7.7 for casein and 6.5 for sodium caseinate. Optimum hydrolysis conditions of fruit bromelain towards haemoglobin showed a sharp peak at an acidic pH 2.9 at 37 degrees C. The lowest results of K-m and the highest results of V-max/K-m, were found for azocasein and azoalbumin. These substrates are highly recommended for fruit bromelain activity determination. (C) 2011 Published by Elsevier Ltd.