Forsee W T, Springfield J D, Schutzbach J S
J Biol Chem. 1982 Sep 10;257(17):9963-7.
An alpha-1,2-mannosidase has been solubilized and partially purified from rabbit liver microsomes (Forsee, W. T., and Schutzbach, J. S. (1981) J. Biol. Chem. 256, 6577-6582). The partially purified enzyme was activated by the addition of zwitterionic phospholipids but maximal activity was found to be relatively independent of acyl chain length or degree of unsaturation. Titration of the enzyme with increasing concentrations of water-soluble and long acyl chain phospholipids demonstrated that an ordered lipid structure of either micelles or bilayers was required for alpha-mannosidase activity. Mixed micelles of Triton X-100 and zwitterionic phospholipids also activated the enzyme. The concentration of phospholipid in the mixed micelles required for activation was dependent upon acyl chain length, but maximal activity was unaffected by this parameter. The addition of negatively charged phospholipids not only failed to activate the enzyme but also inhibited alpha-mannosidase activity in the presence of zwitterionic phospholipids. Inhibition by negatively charged phospholipids was pH dependent with maximal inhibition at pH values of 6.0 or lower. These results suggest that the activity of the alpha-1,2-mannosidase could be subject to modulation by the composition and structure of the microsomal membranes.
一种α-1,2-甘露糖苷酶已从兔肝微粒体中溶解并部分纯化（福尔西，W.T.，和舒茨巴赫，J.S.（1981年）《生物化学杂志》256，6577 - 6582）。添加两性离子磷脂可激活部分纯化的酶，但发现最大活性相对独立于酰基链长度或不饱和度。用浓度递增的水溶性长酰基链磷脂滴定该酶表明，α-甘露糖苷酶活性需要胶束或双层的有序脂质结构。Triton X - 100与两性离子磷脂的混合胶束也能激活该酶。激活所需混合胶束中磷脂的浓度取决于酰基链长度，但最大活性不受此参数影响。添加带负电荷的磷脂不仅不能激活该酶，而且在存在两性离子磷脂的情况下还会抑制α-甘露糖苷酶活性。带负电荷磷脂的抑制作用依赖于pH值，在pH值为6.0或更低时抑制作用最大。这些结果表明，α-1,2-甘露糖苷酶的活性可能受到微粒体膜组成和结构的调节。
