Biardi L, Krisans S K
Department of Biology, San Diego State University, California 92182, USA.
J Biol Chem. 1996 Jan 19;271(3):1784-8. doi: 10.1074/jbc.271.3.1784.
We have recently demonstrated that mevalonate kinase and farnesyl diphosphate (FPP) synthase are localized predominantly in peroxisomes. This observation raises the question regarding the subcellular localization of the enzymes that catalyze the individual steps in the pathway between mevalonate kinase and FPP synthase (phosphomevalonate kinase, mevalonate diphosphate decarboxylase, and isopentenyl diphosphate isomerase). These enzyme are found in the 100,000 x g supernatant fraction of cells or tissues and have been considered to be cytoplasmic proteins. In the current studies, we show that the activities of mevalonate kinase, phosphomevalonate kinase, and mevalonate diphosphate decarboxylase are equal in extracts prepared from intact cells and selectively permeabilized cells, which lack cytosolic enzymes. We also demonstrate structure-linked latency of phosphomevalonate kinase and mevalonate diphosphate decarboxylase that is consistent with a peroxisomal localization of these enzymes. Finally, we show that cholesterol biosynthesis from mevalonate can occur in selectively permeabilized cells lacking cytosolic components. These results suggest that the peroxisome is the major site of the synthesis of FPP from mevalonate, since all of the cholestrogenic enzymes involved in this conversion are localized in the peroxisome.
我们最近证明，甲羟戊酸激酶和法呢基二磷酸（FPP）合酶主要定位于过氧化物酶体。这一观察结果引发了一个问题，即催化甲羟戊酸激酶和FPP合酶之间途径中各个步骤的酶（磷酸甲羟戊酸激酶、甲羟戊酸二磷酸脱羧酶和异戊烯基二磷酸异构酶）的亚细胞定位情况。这些酶存在于细胞或组织的100,000×g上清液组分中，一直被认为是细胞质蛋白。在当前研究中，我们发现，在从完整细胞和缺乏胞质酶的选择性通透细胞制备的提取物中，甲羟戊酸激酶、磷酸甲羟戊酸激酶和甲羟戊酸二磷酸脱羧酶的活性是相等的。我们还证明了磷酸甲羟戊酸激酶和甲羟戊酸二磷酸脱羧酶与结构相关的潜伏性，这与这些酶定位于过氧化物酶体是一致的。最后，我们表明，在缺乏胞质成分的选择性通透细胞中，由甲羟戊酸合成胆固醇是可以发生的。这些结果表明，过氧化物酶体是由甲羟戊酸合成FPP的主要场所，因为参与这种转化的所有胆甾醇生成酶都定位于过氧化物酶体。
