Slomiany B L, Liau Y H, Carter S R, Zielenski J, Slomiany A
Arch Oral Biol. 1986;31(7):463-8. doi: 10.1016/0003-9969(86)90020-8.
The enzymic activity which catalyses transfer of palmitic acid from palmitoyl coenzyme A to mucus glycoprotein was found in Triton X-100 extracts of the microsomal fraction of rat submandibular and sublingual salivary glands. The acyltransferase activity of this fraction was 1.3-1.4 times greater in submandibular gland than in sublingual gland. Further subcellular fractionation of submandibular gland showed that the enzyme activity was associated with a Golgi-rich membrane fraction. Optimum enzyme activity for fatty acylation of mucus glycoprotein was at pH 7.4 using 0.5 per cent Triton X-100, 2 mM dithiothreitol 25 mM NaF and 10 mM MgCl2; higher concentrations were inhibitory. The apparent Km of the submandibular microsomal enzyme for mucus glycoprotein was 5.9 X 10(-7) M, and for palmitoyl-CoA, 3.3 X 10(-5) M. The 14C-labelled glycoprotein product of the reaction co-migrated on CsCl equilibrium, density-gradient centrifugation with submandibular mucus glycoprotein, and contained ester-bound palmitic acid. The fatty acyltransferase showed no activity with proteolytically-degraded glycoprotein; the acceptor capacity of reduced and S-carboxymethylated glycoprotein was only about 10 per cent lower than that of the intact mucus glycoprotein. This suggests that the acylation of salivary mucus glycoprotein with fatty acids occurs at its non-glycosylated, proteolysis-susceptible regions, and that the majority of these fatty acids are linked to the glycoprotein through hydroxyl esters.
在大鼠下颌下腺和舌下腺微粒体部分的Triton X-100提取物中发现了催化棕榈酸从棕榈酰辅酶A转移至黏液糖蛋白的酶活性。该部分的酰基转移酶活性在下颌下腺中比在舌下腺中高1.3 - 1.4倍。对下颌下腺进行进一步的亚细胞分级分离表明，酶活性与富含高尔基体的膜部分相关。使用0.5% Triton X-100、2 mM二硫苏糖醇、25 mM氟化钠和10 mM氯化镁时，黏液糖蛋白脂肪酰化的最佳酶活性在pH 7.4；更高浓度具有抑制作用。下颌下微粒体酶对黏液糖蛋白的表观Km为5.9×10⁻⁷ M，对棕榈酰辅酶A为3.3×10⁻⁵ M。反应的¹⁴C标记糖蛋白产物在CsCl平衡密度梯度离心中与下颌下黏液糖蛋白共迁移，并含有酯结合的棕榈酸。脂肪酰转移酶对经蛋白水解降解的糖蛋白无活性；还原和S-羧甲基化糖蛋白的受体能力仅比完整黏液糖蛋白低约10%。这表明唾液黏液糖蛋白与脂肪酸的酰化发生在其非糖基化、易受蛋白水解的区域，并且这些脂肪酸中的大多数通过羟基酯与糖蛋白相连。
