The gel electrophoresis system presented here allows the separation of proteins with the concomitant retention of detectable native activities. The system, referred to as CAT gel electrophoresis, uses the detergent cetyltrimethylammonium bromide in combination with a discontinuous gel matrix to resolve protein mixtures into discrete bands. Many proteins retain detectable levels of native activity after CAT electrophoresis, and gel bands can be easily identified using assays based on specific enzymatic activities or binding characteristics. The ability to identify protein bands based on Both M(r) and activity in a single gel makes the CAT system a powerful adjunct to existing biochemical techniques.