Changes in hydrolysis specificities of lipase from Rhizomucor miehei to polyunsaturated fatty acyl ethyl esters in different aggregation states

Hydrolysis specificities of lipase from Rhizomucor miehei were compared for various fatty acyl ethyl esters. Activity yields of immobilized lipases, measured with 1 mM substrate, were more than 100%. Differences in hydrolysis rate and affinity for the substrates between lipase preparations were also typically higher during hydrolysis of substrates at 100 mM than at 1 mM, indicating better mass transfer effects for 1-mM substrates. The native lipase showed higher affinity for polyunsaturated fatty acid substrates at 1 mM than at 100 mM. Hydrolysis rates for 1-mM substrates were observed with immobilized lipases, fixed on anion exchange resin with glutaraldehyde and on cation exchange carrier with carbodiimide, and suggested some modification of the basic amino acid related to the lid of R. miehei lipase. Activation with these bifunctional reagents was not observed for 100-mM substrates, indicating that interfacial activation always occurred because of aggregation of 100-mM substrates. These results show that lipase from R. miehei recognizes molecular aggregation of lipids, and that various changes occur in the hydrolysis specificities for fatty acids.