Characteristics and Activity Changes of Polygalacturonase during Maturation and Postharvest of Persimmon Fruits

감과실의 성숙과 추숙중의 Polygalacturonase활성 변화 및 특성

Polygalacturonase activity was not detected at turning stage but were 55.01 and 206.70 units/100g -fr. wt. in mature and soft persimmon, respectively. Polygalacturonase have two isoenzymes and its molecular weight was estimated to be 55,000 doltons by the method of gel filtration. Vmax and Km of polygalacturonase 1 were 0.195$\mu$ mole reducing-sugar/$m\ell$/30 min. and 3.50mg/$m\ell$, respectively. The optimum temperature and pH of the enzyme appeared to 4$0^{\circ}C$ and 3.5, respectively. Polygalacturonase I had Vmax of 0.110m mo1e reducing-sugar/$m\ell$/30min. and Km value of 2.50mg/$m\ell$, The optimum temperature and pH of polygalcturonase II appear 4$0^{\circ}C$ and 4.0, respectively. Polygalacturonase I was fairly stable at 6$0^{\circ}C$while polygalacturonase II appeared to be stable up to 4$0^{\circ}C$.

Polygalacturonase의 활성은 미숙감과실에서 나타나지 않았으나 완숙감과 연시에서 각각 55.01. 206.70unit/100g-fr. wt.로 연시에서 급격히 증가하였다. 연시에서 추출한 polygalacturonase의 isoenzyme은 2종이었고, 분자량은 다같이 55,000 dal-ton이었다. Polygalacturonase isoenzyme의 특성을 조사한 결과, polygalacturonase I의 Vmax는 0.195$\mu$ mole reducing-sugar/$m\ell$/30min., Km값은 3.50mg/$m\ell$이었고, 최적온도 4$0^{\circ}C$, 최적 pH 3.5이었으며, 열처리시 6$0^{\circ}C$까지 안정하였다. Polygalacturonase II 의 Vmax는 0.11$\mu$mole reducing-sugar /$m\ell$/30min., Km값은 2.50mg/$m\ell$이었고, 최적 온도와 pH는 35$^{\circ}C$와 4.0이었으며. 4$0^{\circ}C$까지 안정하였다. Polygalacturonase I 과 II는 K+, Cu++, Zn++, SDS, EDTA에 의해서 활성이 저해되었고 Ca++ 의해 다소 촉진되었다.