Octopine Dehydrogenase In The Adductor Muscle Of Live Scallop And Its Changes During Postharvest

To investigate the quality change mechanism of postharvest commercial bivalves,octopine dehydrogenase（ODH）,a glycolytic enzyme exists only in invertebrates,was selected to explore the metabolic changes of live Yesso scallop（Patinopecten yessoensis）.This research focused on the ODH extracted from adductor muscle.The metabolic response of ODH under air exposure and the enzymatic properties were studied.Furthermore,the ODH activity extracted from different tissues（striated muscle,smooth muscle,gill,mantle,digestive gland and gonad）under simulated live products storage was also investigated.（1）The distribution of opine dehydrogenase（OpDHs）and the enzymatic property of ODH:the ODH extracted from fresh live scallops was investigated.ODH was the predominant OpDHs in adductor muscle of scallops and its activity was higher than other OpDHs and LDH.The optimal pH and temperature of ODH were approximately 6.5 and 40℃,respectively.ODH activity was inhibited by Ca²⁺,Mg²⁺,Mn²⁺,Cu²⁺and Fe³⁺.Succinate,acetate,propionate and ATP inactivated ODH to some extent of which succinate is the strongest inhibitor followed by ATP.And an extract of ODH with protein about 40 KDa as the main components from adductor muscle was obtained.（2）The changes of ODH activity under air exposure during postharvest:the changes of ODH activity and energy metabolites in adductor muscle under air exposure were analyzed.Compounds involved in energy metabolism,comprising pH,ATP-related compounds,phosphate arginine（PA）,and free amino acid（FAA）were decreased under air exposure which indicated the disturbance of normal metabolism.Arginine and aspartic acid decreased,and at the same time,the accumulation of succinate with the decrease of malic acid and fumaric acid indicated the start of anaerobic metabolism.Then the change of ODH activity under air exposure was investigated.ODH activity in response to aerial exposure was found and the response increased when the environmental stress was enhanced.In general,there was a positive response of ODH activity to dry storage and supported a potential indicator relating to the quality mechanism for post-harvest live scallop.（3）Changes of ODH activity under simulated live products storage:the ODH activity extracted from different tissues（striated muscle,smooth muscle,gill,mantle,digestive gland and gonad）under simulated live products storage was also investigated.Four simulated live products storage conditions including wet storage with oxygen,wet storage without oxygen,dry storage with oxygen package and dry storage covered with wet cloth,were carried out to explore the changes of ODH in different tissues.ODH activity was much higher in adductor muscle than other tissues.The ODH activity of wet storage decreased after the initial fluctuation.And the ODH activity of dry storage increased with the storage time.However,with or without oxygen supply had no effect on the ODH activity.The ODH response in gonad was like muscle tissues.However,the ODH activity in gill,mantle and digestive gland is very low and without obvious regularity.