The major form of glycerol phosphate dehydrogenase in human heart (GPDH-1) is a minor form (less than 15%) in brain and other tissues and is extremely labile. After GPDH-1 was eluted from an agarose column to which Cibacron blue F3GA had been covalently linked, (a) it was no longer labile (t 1/2 at 40 degrees C changed from 1.6 min to greater than 180 min); (b) it could now be stained for activity on native gels following electro-phoresis; and (c) it now migrated with the bromphenol blue dye front. The results suggest that this stabilized form of GPDH-1 is due to the covalent binding of charged ligands from the column and that this technique may be useful for studying the molecular structure and/or the active site of GPHD-1 and possibly of other enzymes which bind to blue agarose.