Gelman A, Kuz'mina V, Drabkin V, Glatman L
Fishery Products Laboratory, Kimron Veterinary Institute, P.O. Box 12, Bet Dagan 50250, Israel.
Comp Biochem Physiol B Biochem Mol Biol. 2003 Oct;136(2):323-9. doi: 10.1016/s1096-4959(03)00213-6.
Three kinds of boreal zone fish were investigated for gastrointestinal glycyl-L-leucine (GL) dipeptide cleaving activity as a function of feeding stage and seasonal changes. The enzyme activity tested in the perch (Perca fluviatilis L.) intestine increased steadily during digestion and rapidly disappeared after completion. The temperature characteristics and the seasonal changes in dipeptide cleaving activity in pike perch (Stizostedion lucioperca L.) and bream (Abramis brama L.) were studied. In summer, the maximal activities in the pike perch and the bream were found at temperatures of 40 and 30 degrees C, respectively. In winter, the temperature of maximal activity in pike perch fell to only 30 degrees C, whereas no changes were observed in bream. The activation energies in bream and pike perch were several times lower in winter than in summer. Seasonal changes in the dipeptide cleaving activity at low temperature relative to that at the temperature of maximal activity were found. At high temperatures, the stability of the enzyme decreases in winter and increases in summer, but in the presence of a substrate the thermal stability of the enzyme increases both in winter and in summer. In our experiments, we found that in these fish, GL dipeptidase was unstable at 0 and -10 degrees C.
研究了三种北方鱼类胃肠道中甘氨酰-L-亮氨酸（GL）二肽裂解活性与摄食阶段和季节变化的关系。在鲈鱼（Perca fluviatilis L.）肠道中检测到的酶活性在消化过程中稳步增加，消化完成后迅速消失。研究了梭鲈（Stizostedion lucioperca L.）和鲷鱼（Abramis brama L.）中二肽裂解活性的温度特性和季节变化。夏季，梭鲈和鲷鱼的最大活性分别出现在40℃和30℃。冬季，梭鲈最大活性温度仅降至30℃，而鲷鱼未观察到变化。冬季鲷鱼和梭鲈的活化能比夏季低几倍。发现了低温下二肽裂解活性相对于最大活性温度下的季节性变化。在高温下，酶的稳定性在冬季降低，在夏季增加，但在有底物存在的情况下，酶的热稳定性在冬季和夏季均增加。在我们的实验中，我们发现这些鱼类中的GL二肽酶在0℃和-10℃时不稳定。
