Fructose 1,6-bisphosphate aldolase is a heparin-binding protein

Proteins with affinity to heparin under physiological conditions were isola ted from bovine cerebral cortex. First, the extract of cerebral cortex was applied to a chondroitin polysulfate column under physiological conditions. Then, the pass-through fraction was applied to a heparin column. Among the bands on SDS polyacrylamide gel electrophoresis of the fraction bound to t he heparin column, the major one was identified as fructose 1,6-bisphosphat e aldolase (FPA), a cytosolic enzyme involved in the glycolytic pathway. Th e results indicated that FPA is a heparin-binding protein which exhibits no affinity to chondroitin polysulfate. The results of affinity chromatograph ies revealed that FPA binds to intact heparin and modified heparins desulfa ted at C2 OH of the iduronic acid residue or at Cg OH or C2 NH, of the gluc osamine residue. When 6-O-desulfated heparin was employed as the affinity l igand, a single peak having FPA activity was isolated from the extract of b ovine cerebral cortex. By further Mono Q chromatography and Superdex gel-fi ltration, five isoenzymes were purified with more than 50% recovery, These isoenzymes were identified as FPA A4, A3C1, A2C2, A1C3, and C4 by native el ectrophoresis with and without 4 M urea and subsequent amino acid sequence analysis. The use of 6-O-desulfated heparin affinity chromatography thus fa cilitated the purification of FPA.