Adhikari H R, Vakil U K
Biochim Biophys Acta. 1980 Dec 15;633(3):465-78. doi: 10.1016/0304-4165(80)90204-4.
A significant decrease in total carbohydrates and particularly in mannose, galactose and sialic acid has been observed in vitamin A-deficient rat liver lysosomal membrane. These alterations adversely affect the membrane permeability and structure-linked latency of the lysosomal enzymes. Significant reduction in the pH-dependent in vitro binding of the lysosomal arylsulfatase B to the highly purified membrane has been observed in vitamin A deficiency. This is attributed to the decrease in electro-negativity, mainly due to the observed reduction in negatively-charged sialic acid residues on the outer side of the membrane. Similar reduction in sialic acid content on the inner side of the membrane affects the microenvironment in the lysosomes. Intralysosomal pH, measured by computing the proteolytic activity of lysed lysosomes and of phagolysosomes, endocytosed with denatured 131I-labelled human serum albumin, is slightly consistently higher in vitamin A-deficient groups compared to that in control alone. This is reflected in the low rate of degradation of the entrapped proteins in vitamin A deficiency. The possible physiological significance of the observations is discussed with special reference to the loss of surface carbohydrates, particularly sialic acid, in vitamin A-deficient rats.
在维生素A缺乏的大鼠肝脏溶酶体膜中，已观察到总碳水化合物，尤其是甘露糖、半乳糖和唾液酸显著减少。这些改变对溶酶体酶的膜通透性和与结构相关的潜伏性产生不利影响。在维生素A缺乏的情况下，已观察到溶酶体芳基硫酸酯酶B与高度纯化膜的pH依赖性体外结合显著降低。这归因于电负性的降低，主要是由于观察到膜外侧带负电荷的唾液酸残基减少。膜内侧唾液酸含量的类似减少会影响溶酶体内的微环境。通过计算用变性的131I标记人血清白蛋白内吞的裂解溶酶体和吞噬溶酶体的蛋白水解活性来测量的溶酶体内pH值，在维生素A缺乏组中与单独对照组相比略有一致地更高。这反映在维生素A缺乏时被困蛋白质的低降解率上。特别参考维生素A缺乏大鼠表面碳水化合物，尤其是唾液酸的损失，讨论了这些观察结果可能的生理意义。
