Valencia orange로부터 분리된 TLPE는 분자량이 36 KD(37.5 KD)이며 등전점이 pH 8.4, 8.7, 8.9, 9.8, ${geq}10$인 isoenzyme의 혼합물이었고, 또한 TSPE는 분자량이 53 KD(50 KD)이며 등전점이 pH 8.7, 9.2, ${geq}10$인 isoenzyme의 혼합물이었다. TLPE의 최적 작용 pH는 $7.0,;appK_{M}$은 1.1 mg/ml, appVmax는 $0.53;{mu}mol/min/{mu}g$, turnover number는 19,000 mol/mol/min이었으며, TSPE의 최적 작용 pH는 $7.0{sim}8.5,;appK_{M}$은 1.7 mg/ml, appVmax는 $1.01;{mu}mol/min/{mu}g$, turnover number는 54,000 mol/mol/min이었다. TSPE는 가열처리와 오렌지쥬스에서의 저장에 대하여 TLPE보다 훨씬 안정하였다. 또한 PE조효소, TSPE 그리고 TLPE 중에서는 orange juice의 cloud loss에 PE조효소가 가장 크게 영향을 미쳤으며 그 다음으로 TSPE TLPE 순서로 나타났다.
This study was carried out to characterize thermolabile pectinesterase (TLPE) and thermostable pectinesterase (TSPE) separated from crude PE of Valencia orange in order to investigate the preventive measures of cloudy juice clarification. The TLPE was observed to be mixture of several isoenzymes with the same molecular weight of 36 KD (37.5 KD) but different isoelectric point of pH 8.4, 8.7, 8.9, 9.8 and ${geq}10$ which were unstable at $70^{circ}C$, and the TSPE also was found to be mixture of two or three isoenzymes with the same molecular weight of 53 KD (50 KD) but different isoelectric point of pH 8.7, 9.2 and ${geq}10$ which had slightly different stability from one another at $70^{circ}C$. The TLPE and the TSPE had the optimum reaction pH of 7.0 and $7.0{sim}8.5,;appK_{M}$ of 1.1 and 1.7 mg/ml, appVmax of 0.53 and $1.01;{mu}mol/min/{mu}g$, and the turnover number of 19.000 and 54,000 mol/mol/min toward Kodak pectin, respectively. The TSPE had higher storage stabiblity and cloud loss effect on orange juice than the TLPE. Above all, the crude PE was most effective on orange juice cloud loss among the PEs used.
