Sephadex-bound histamine in the catalysis of ester hydrolysis

Ester hydrolysis by Sephadex-bound catalysts was studied in a flow-through system. Three different immobilized preparations were synthesized and used: histamine-, coimmobilized histamine-octylamine-, and octylamine-Sephadex; octylamine-Sephadex was used as a reference. Immobilization was carried out using water-soluble carbodiimide, which gave amide linkages between carboxymethyl Sephadex and the groups attached. It was found that the coimmobilized histamine-octylamine preparation was three times more efficient than immobilized histamine alone in the hydrolysis of the esterp-nitrophenylcaproate, whereas hardly any difference was found in the hydrolysis of the less hydrophobic substratep-nitrophenylacetate. We attribute this enhancement of the hydrolysis ofp-nitrophenylcaproate to local enrichment of the substrate on the histamine-octylamine matrix caused by the presence of hydrophobic octyl groups.