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 °C), casein and sodium caseinate (pH 2–10 at 20–70 °C), and haemoglobin (pH 2–6.5 at 30–60 °C). Fruit bromelain has shown optimum activity at pH 7.5 for azoalbumin and at 6.5 for azocasein, all at 55 °C. Fruit bromelain activity determined with casein and sodium caseinate has shown optimum activity at 59 °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 °C. The lowest results of Km and the highest results of Vmax/Km were found for azocasein and azoalbumin. These substrates are highly recommended for fruit bromelain activity determination.