松墨天牛纤维素酶的研究 I.纤维素酶性质研究

Study on the Character of Cellulase in Monochamus alternatus

以松墨天牛幼虫为实验材料,研究了其肠道内纤维素酶的组成和酶解动力学特征等。结果表明,松墨天牛幼虫肠道内有完整的纤维素酶系,其中以C1酶活性最强,Cx酶次之,β l,4 葡萄糖苷酶活性最弱;C1酶、Cx酶和β 葡萄糖苷酶3者的最适作用温区分别为35～55、45～55、40～50℃,最适pH值分别为5 0、5 6、5 0;Cx酶具有最强的热稳定性(65℃,2h),C1酶次之(55℃,2h),β l,4 葡萄糖苷酶最低(50℃,1h)。此外动力学参数比较揭示,C1酶具有最大的Vmax和Km,分别为1 0838和0 7632,β l,4 葡萄糖苷酶和Cx酶分别具有最小的Km(0 1832)和Vmax(0 4339),但β 萄糖苷酶具有最大的酶解初速度(0 5938)。

Monochamus alternatus is one of the most perilous wood-boring insect pests in pine plantations in southern China, and the enzyme cellulase plays the major function to digest the ingested woody tissue in its gut.The cellulase extracted from larvae of M.alternatus was tested to determine its constitution and kinetic properties in this paper.The results revealed that the longicorn borers had integrated cellulolytic enzyme complex: endo-β-1,4-glucanase (Cx-ase),exo-β-1,4-glucanase (C_1-ase) and β-1,4-glucosidase in their gut, among which the activity of C_1-ase was the strongest, and β-1,4-glucosidase the weakest.For C_1-ase, Cx-ase and (β-1,4-glucosidase),the optimum temperature range was between 35～55 ℃, 45～55 ℃ and 40～50 ℃ respectively, while their optimum pH at 5.0,5.6 and 5.0. Besides, Cx-ase had the stronger stability to heat,which still had strong activity after being heated at 65 ℃ for 2 h. After comparison of the kinetic parameters among the cellulases of M. alternatus,it was found that C_1-ase had greater V_(max) and K_m,which was 1.083 8 and 0.763 2 respectively,however,β-1,4-glucosidase had greater relatively muzzle velocity.