Changes in Sugar Content and Invertase Activity in Plum Fruits during the Maturation

자두과실(果實)의 성숙중(成熟中) 당함량(糖含量) 및 Invertase의 활성변화(活性變化)

The changes of sugar content and invertase activity during maturation of plum fruits, and properties of the enzyme were investigated in this study. The soluble sugars in plum fruits were mainly sucrose, glucose and fructose. The sucrose content in the fruit increased slowly at the early stage of maturation and then decreased slightly. At the final stage, the sucrose content increased remarkably with maturation. The contents of glucose and fructose increased slowly at the early stage of maturation following decrement at middle stage. At the final stage, glucose content decreased continuously while fructose content increased again following decrement. Invertase activity in the fruit increased during maturation showing maximum at the onset of color change and after that, decreased remarkably. The optimum pH and temperature of invertase activity were pH 5.0 and $65^{\circ}C$, respectively. The enzyme was most stable at pH 5.0 and retained 75% of its activity after incubation at $70^{\circ}C$ for 15min. The enzyme was activated by $Cu^{{+}{+}}$, $Ca^{{+}{+}}$, but inhibited by $Hg^{{+}{+}}$ remarkably.

성숙 중 자두 과실의 당함량 및 invertase활성 변화와 효소학적 성질에 대하여 조사한 결과는 다음과 같다. 자두과실에 함유되어 있는 soluble sugar의 대부분은 sucrose, glucose 및 fructose이었다. 성숙 중 sucrose의 함량은 초기에는 서서히 증가하다가 그 이후 약간 감소하며 성숙말기에는 급격히 증가하였다. Glucose와 fructose는 성숙초기에는 완만히 증가하였으나, 그 이후 glucose는 감소, fructose는 증가하는 경향이었다. Invertase의 활성은 성숙함에 따라 증가하여 색깔의 변화가 일어나는 시기에 최고의 활성을 나타냈으며, 그 이후 급격히 감소하였다. 효소의 최적 pH와 온도는 각각 5.0과 $65^{\circ}C$였다. pH와 열안정성은 pH 5.0부근에서 안정하였으며, $70^{\circ}C$, 15분간에서 약 75% 잔존활성을 가졌다. 효소 활성은$Ca^{{+}{+}}$, $Cu^{{+}{+}}$에 의해 증가되었으나 $Hg^{{+}{+}}$에 크게 저해되었다.