Abstract
Only a single phosphofructokinase isoenzyme is present in the mucosa of rat small intestine. Mucosal phosphofructokinase was purified to yield a homogeneous preparation of specific activity 175 units/mg of protein. The native enzyme is a tetramer, with monomer M sub(r) 84,500 plus or minus 5000. The native enzyme may be degraded by the action of endogenous proteinases to give two products with the same specific activity as the native enzyme: degradation occurs in the order native enzyme arrow right proteolytic product 1 arrow right proteolytic product 2. Purified native mucosal phosphofructokinase displayed little co-operativity with respect to fructose 6-phosphate at pH 7.0 and was only weakly inhibited by ATP.