Abstract
We have developed methods for the isolation of Golgi apparatus from a number of mammalian tissues. The Golgi is distinct both chemically and enzymatically from the other membranes of the cell. For both liver and kidney, galactosyltransferase has been found to be a useful marker enzyme for Golgi membranes. This enzyme is involved in the modification of glycoproteins during secretion. In addition to lipoproteins and glycoproteins, the Golgi apparatus of liver is involved in the secretion of albumin, a simple protein. It does not, however, take part in the synthesis of sphingomyelin, lecithin, or triglycerides which are present in the secreted lipoproteins. These lipids appear to be synthesized predominantly by the endoplasmic reticulum. In kidney, which is rich in glycolipids, 3โฒโphosphoadenosine 5โฒโphosphosulfate, an enzyme which converts cerebroside to sulfatide, is localized predominantly in the Golgi apparatus. Thus, Golgi functions to modify glycolipids as well as mucopolysaccharides and proteins. Sulfatide constitutes a significant fraction of the total lipid of both Golgi and plasma membranes of kidney. When ^35^Sโsulfate is injected into rats, it is incorporated first into the sulfatides of the Golgi apparatus and later appears in the sulfatides of the plasma membrane. The data are consistent with the view that sulfatides are formed in the Golgi apparatus of kidney and then transported to the plasma membrane.