A study of glycerolphosphate acyltransferase in rat liver mitochondria-submitochondrial localization and some properties of the solubilized enzyme |
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| Institution: | 1. Virginia Tech, School of Animal Sciences, Blacksburg, VA 24061, USA;2. Department of Animal Science, College of Animal Science and Food Engineering, University of São Paulo, Pirassununga, SP 13635-900, Brazil;3. Agriculture and Agri-Food Canada, 6000 C & D Trail, Lacombe, Alberta T4L 1W1, Canada;4. USDA-ARS, Roman L. Hruska US Meat Animal Research Center, Clay Center, NE 68933, USA;1. Department of Nutrition, Dietetics and Food Sciences, Utah State University, Logan, UT 84322, United States;2. Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, UT 84322, United States;3. School of Animal Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, United States |
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| Abstract: | - 1.1. Glycerolphosphate acyltransferase (GPAT) was solubilized from the rat liver mitochondrial membranes using sodium cholate. Dithiothreitol was necessary to stabilize the solubilized enzyme on storage.
- 2.2. Unlike the enzyme in situ in mitochondrial membranes, the solubilized mitochondrial GPAT was susceptible to inhibition by N-ethylmaleimide; a property more characteristic of the distinct microsomal form of GPAT.
- 3.3. Solubilized mitochondrial GPAT retained its very high preference for saturated acyl-CoA substrate (palmitoyl-CoA) and had no activity whatever with any tested concentration of the unsaturated substrate oleoyl-CoA.
- 4.4. Solubilization increased the affinity of mitochondrial GPAT for palmitoyl-CoA whilst decreasing the Km for glycerol phosphate.
- 5.5. After separation of liver mitochondrial outer and inner membranes and estimation of cross-contamination by appropriate markers it was concluded that the mitochondrial inner membrane contains significant GPAT activity. This was established with preparations from fed, 48 hr-starved and streptozotocin-diabetic rats.
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