Ohue M, Makita T
Department of Veterinary Anatomy, Faculty of Agriculture, Yamaguchi University, Japan.
J Vet Med Sci. 1994 Apr;56(2):329-33. doi: 10.1292/jvms.56.329.
Carnitine acetyltransferase (CAT), an enzyme involved in the beta-oxidation of fatty acids, was localized in the interscapular brown adipose tissue of the rat. The reaction products were localized on the cristae and surface of the inner mitochondrial membrane. Thin needle-like reaction products were abolished in control specimens incubated in either acetyl CoA (substrate)-free medium or inhibitor (HgCl2)-containing medium. They were also abolished when materials were fixed in a mixture of glutaraldehyde (1%) and paraformaldehyde (4%). Even when cristae were disintegrated in certain mitochondria contacting with nearby lipid droplets, the CAT activity was preserved in the rest of the intact cristae. However, when a mitochondrion was completely engulfed in a lipid globule, all cristae lost their CAT activity. These findings suggest an influence of lipid on the mitochondrial CAT activity. In the experimental administration of bezafibrate, a hypolipidemic drug increasing the CAT activity, the CAT activity in the brown adipose tissue was significantly increased (male 6.0-fold, female 2.0-fold) at two weeks of administration of bezafibrate except for castrated male and female rats. However, the localization of CAT activity in mitochondria was not altered by the administration of bezafibrate.
肉碱乙酰转移酶（CAT）是一种参与脂肪酸β氧化的酶，定位于大鼠肩胛间棕色脂肪组织中。反应产物定位于线粒体内膜的嵴和表面。在不含乙酰辅酶A（底物）的培养基或含抑制剂（HgCl2）的培养基中孵育的对照标本中，细针状反应产物消失。当材料用戊二醛（1%）和多聚甲醛（4%）的混合物固定时，它们也会消失。即使在某些与附近脂滴接触的线粒体中嵴解体时，完整嵴的其余部分仍保留CAT活性。然而，当一个线粒体完全被一个脂质球吞没时，所有嵴都失去了CAT活性。这些发现表明脂质对线粒体CAT活性有影响。在使用增加CAT活性的降血脂药物苯扎贝特进行实验给药时，除去势的雄性和雌性大鼠外，在给药两周时棕色脂肪组织中的CAT活性显著增加（雄性增加6.0倍，雌性增加2.0倍）。然而，苯扎贝特的给药并未改变线粒体中CAT活性的定位。
