Pectinesterase (PE) activity can be determined by several methods. Some determine the changes in the substrate (titration of the carboxyl groups, recording pH changes, colour change of pH indicator, gelation & viscosity and manometric assay), others measure the methanol liberated (colour reactions & titrations, gas chromatography and use of radioisotopes). Previous kinetics studies on the PE from Carica papaya have mostly used the titration method described. However, the present research attempts to assess the enzyme properties of papaya PE using a spectrophotometric method. PE isolated from papaya was investigated to determine its optimum pH and temperature. Optimum pH and temperature were estimated to be 7.4 and 75?C, respectively. Kinetic parameters of the enzyme (Km and Vmax values) were evaluated by both titrimetric and spectrophotometric methods. The Km value of 3.06 mg/ml and Vmax of 2.2070 PE units/ml was obtained with the titration method. Whereas the spectrophotometric method gave a Km value of 3.43 mg/ml and Vmax of 0.0456 μmol/min. The effect of modulators on PE activity was also studied. It was observed that aluminium chloride and sodium bisulphite caused an increase and sodium bicarbonate decreased the Km value while calcium chloride and citric acid had negligible effect.
Share this article