Some Characteristics of Iron-Catalyzed Nadh-Dependent Sarcoplasmic Reticular Lipid Oxidation in a Seawater Clam (Meretrix Lusoria) and Freshwater Clam (Corbicula Fluminea)

Abstract

Characteristics of an iron‐catalyzed enzymic lipid oxidation system requiring nicotinamide adenine dinucleotide (NADH) as the reducing agent in the sarcoplasmic reticulum (SR) of clams were investigated. For both the seawater and freshwater clams, the system preferred NADH to NADPH as the reducing agent (P < 0.05). Lipid oxidation activities of the SR were significantly reduced (P < 0.05) when reaction temperature reached 45 and 65C for the freshwater clam and seawater clam, respectively, indicating that denaturation of the enzymes had occurred. When reaction pH ranged from 6.0 to 7.5, acidic pH tended to amplify the lipid peroxidation activity. Under the same experimental conditions, SR lipid oxidation activities in the seawater clam were greater (P < 0.05) than those in the freshwater clam. The fatty acid composition of SR lipids may have been a factor affecting this outcome as the level of polyunsaturated fatty acids of SR lipids in the seawater clam was higher than that in the freshwater clam. PRACTICAL APPLICATIONS The results of this study enhance our knowledge of the lipid oxidation system at the subcellular level of seawater and freshwater clams. Both of these clams are important cultured species in Taiwan and other Asian countries. Clam culturists can manipulate the fatty acid profiles of the clams by altering the dietary lipid sources during the farming stage, while processors may be able to limit oxidation by avoiding pro‐oxidative conditions.