Van Heusden M C
Department of Biochemistry, University of Arizona, Tucson 85721.
Insect Biochem Mol Biol. 1993 Oct;23(7):785-92. doi: 10.1016/0965-1748(93)90066-2.
Lipoprotein lipase (LpL) activity in Manduca sexta flight muscle tissue was measured using in vivo radiolabeled lipophorin as a substrate. LpL hydrolyses diacylglycerol in the low density lipophorin (that occurs during flight) at a higher rate than diacylglycerol in the high density lipophorin (present in the resting insect). LpL has a pH-optimum of 7.5 and is less sensitive to NaCl than mammalian LpL. LpL is inhibited by bovine albumin and chicken ovalbumin. LpL is inhibited by the serine protease inhibitors diisopropylfluorophosphate (DFP) and phenylmethanesulfonyl fluoride (PMSF), which indicates the presence of an active site serine similar to mammalian LpL. Flight muscle LpL shows affinity for immobilized copper as well as for immobilized heparin. Using radiolabeled DFP, a protein of 37 kDa was identified (after SDS-PAGE) as the DFP-binding protein in a partially purified preparation of LpL. This 37 kDa protein is proposed to be the LpL or a subunit thereof.
利用体内放射性标记的脂转运蛋白作为底物，测定了烟草天蛾飞行肌组织中的脂蛋白脂肪酶（LpL）活性。LpL水解低密度脂转运蛋白（在飞行期间出现）中的二酰甘油的速率高于高密度脂转运蛋白（存在于静止昆虫中）中的二酰甘油。LpL的最适pH为7.5，且与哺乳动物LpL相比，对NaCl的敏感性较低。LpL受到牛血清白蛋白和鸡卵清蛋白的抑制。LpL受到丝氨酸蛋白酶抑制剂二异丙基氟磷酸酯（DFP）和苯甲基磺酰氟（PMSF）的抑制，这表明存在与哺乳动物LpL类似的活性位点丝氨酸。飞行肌LpL对固定化铜以及固定化肝素表现出亲和力。使用放射性标记的DFP，在LpL的部分纯化制剂中（SDS-PAGE后）鉴定出一种37 kDa的蛋白质为DFP结合蛋白。这种37 kDa的蛋白质被认为是LpL或其亚基。
