Examination of the effects of dry storage stress on mitochondrial energy synthesis in the scallop Mizuhopecten yessoensis

Abstract

Postharvest dry storage was simulated by storing scallops at 4 °C for different durations. The quantification of 40 energy metabolites related to the glycolysis, tricarboxylic acid (TCA) cycle and oxidative phosphorylation pathways in the scallop adductor muscle was performed by LC–MS/MS. The results showed that during the early stage (0–6 h), 6-phosphofructokinase-2 (PFK-2) in glycolysis was inhibited, and the TCA cycle was maintained at a low level. Concurrently, the aspartate pathway and opine pathway were initiated, and alanine and opines were the early metabolites found during this stage. During the middle and late stages (6–12 h) of dry storage, muscle pH decreased. Phosphoenolpyruvate carboxy kinase (PEPCK) was activated, leading to the competitive inhibition of pyruvate synthesis by PEPCK. Phosphoenolpyruvate enters the reverse TCA cycle via the phosphoenolpyruvate → malate pathway to produce succinate. The increase in succinate further induced the succinyl-CoA → propionate pathway, and the end products were acetate and propionate. Alteration of the metabolic pathway was observed, leading to a change in the NADH level. Subsequently, a fluctuating mitochondrial membrane potential was observed. Reimmersion after 6 h of dry storage promoted the recovery of the muscle TCA cycle. Nevertheless, after long-term dry storage (24 h), reimmersion storage did not restore the succinate → oxaloacetate metabolism in the TCA cycle. High-intensity air exposure had a long-term and irreversible effect on mitochondrial energy metabolism. Therefore, it is concluded that the dynamics of mitochondrial metabolism may be sensitive to dry exposure during postharvest operations.