不同表面活性剂条件下脂肪酶GZEL的催化行为

Catalytic Behaviors of Gibberella zeae Lipase(GZEL)in the Presence of Different Surfactants

利用自动电位滴定仪测定脂肪酶GZEL在不同类型及浓度的表面活性剂条件下对该酶脂肪酶活力和磷脂酶活力及其最适反应p H条件的影响,为进一步评估该脂肪酶在洗涤剂工业中的应用价值提供科学指导。研究发现:阴离子型和阳离子型表面活性剂对该酶的脂肪酶活力和磷脂酶活力发挥均起抑制作用,并且随着表面活性剂浓度增加,抑制作用更为显著,高于其临界胶束浓度将导致酶蛋白活力完全丧失;在阴离子型表面活性剂(N-月桂酰肌氨酸钠、十二烷基硫酸钠、脱氧胆酸钠)存在情况下,GZEL发挥磷脂酶活力的最适p H由6.0变为7.0。不同非离子型表面活性剂在低于其各自临界胶束浓度条件下对GZEL酶活力发挥所起调控作用不同:7.0m M浓度条件下,辛基-β-D-吡喃葡萄糖苷使该酶的脂肪酶活力提高(22.97%),磷脂酶活力提高3.11%;而在0.05m M浓度条件下,Triton X-100使该酶脂肪酶活力降低4.05%,磷脂酶活力提升0.14%;在高于Triton X-100临界胶束浓度条件下,酶蛋白仍保留50%左右酶活力,但在高于辛基-β-D-吡喃葡萄糖苷临界胶束浓度条件下,其活性则完全丧失。两性离子型表面活性剂对GZEL酶活力影响最大,导致酶蛋白完全失活。

Effects of different types and concentrations of surfactants on the lipase/activity and phospholipase activity of the Gibberella Zeae lipase(GZEL)and its corresponding optimum pH were examined by automatic potentiometric titration,to provide scientific guidance for further evaluation on the application potential of the lipase in the detergent industry.Results revealed that both anionic and cationic surfactants exerted inhibitory effects on the lipase activity and phospholipase activity of GZEL,and the inhibition increased with an increase of the surfactant concentration,with a surfactant concentration higher than its critical micelle concentration causing the complete loss of the activity of the enzyme protein.In the presence of an anionic surfactant(sodium N-lauroylsarcosinate,sodium dodecyl sulfate(SDS),sodium taurodeoxycholate(NATDC),the optimal pH for the phospholipase activity of GZEL was changed from pH 6.0 to pH 7.0.Different nonionic surfactants had different effects on both activities of GZEL at concentrations lower than their corresponding critical micelle concentrations:At a concentration of 7.0 mM,octyl-β-d-glucopyranoside increased the lipase activity(by 22.97%)and phospholipase activity(by 3.11%)of GZEL,whereas,at 0.05 mM,Triton X-100 reduced the lipase activity(by 4.05%)of GZEL,but increased the phospholipase activity(0.14%)of GZEL.When the concentration of Triton X-100 was higher than its critical micelle concentration,GZEL about 50%of the enzyme activity was still retained,whereas,octyl-β-d-glucopyranoside at a concentration higher than its critical micelle concentration made the activity of GZEL lose completely.Zwitterionic surfactant had the greatest effect on the activity of GZEL,resulting in the complete inactivation of enzyme protein.