Localisation of acetyl-CoA: alpha-glucosaminide N-acetyltransferase in microsomes and lysosomes of rat liver.

Subcellular fractions of rat liver were obtained by differential centrifugation. The fractions enriched in lysosomes or microsomes were further fractionated in discontinuous sucrose density gradients or continuous iso-osmotic gradients made of modified colloidal silica. The fractions were analyzed for marker enzymes of the different subcellular organelles and for acetyl-CoA: alpha-glucosaminide N-acetyltransferase. The acetyl-CoA: alpha-glucosaminide N-acetyltransferase activity showed a bimodal distribution. About one fourth of the activity was associated with lysosomes, whereas the greater part of the activity was recovered in the microsomal fraction. Plasma membrane-enriched fractions contained only trace amounts of acetyl-CoA: alpha-glucosaminide N-acetyltransferase. The lysosomal and microsomal acetyl-CoA: alpha-glucosaminide N-acetyltransferases are membrane-bound and can be solubilized with Triton X-100. The pH dependence and sensitivity to various ions was similar for the lysosomal and microsomal enzyme.