PURIFICATION AND PROPERTIES OF PECTINESTERASE FROM SOURSOP (ANONA-MURICATA) PULP

Two forms of pectinesterase were purified using the techniques of ammo nium sulphate fractionation, ion-exchange chromatography and gel filtr ation. PE I had a specific activity of approximately 4 units mg(-1) (4 3-fold), that of PE II was 6.4 units mg(-1) (229-fold). These pectines terases (PE I and PE II) had approximate molecular weights of 29100 an d 24100, respectively, as estimated by gel filtration, and 31000 and 2 8000, respectively, as estimated by sodium dodecyl sulphate polyacryla mide electrophoresis. The optimum temperature for enzyme activity was shown to be 60 degrees C for both PE I and PE II. The activation energ ies of PE I and PE II were calculated as 36 kJ mol(-1) and 42 kJ mol(- 1), respectively. The optimum pH values for both pectinesterases lie w ithin the range 7.0-8.0. The K-m value for PE I was 0.52 mg ml(-1) and 0.0843 mg ml(-1) for PE II. PE I had a maximum velocity (V-max) of 15 4 mu mol mg(-1) min(-1), and PE II a V-max of 726 mu mol mg(-1) min(-1 ). (C) 1997 Elsevier Science Ltd. All rights reserved.