Paramyosin Distribution Of Mollusks Muscle Protein In Different Commercial Species

Live commercial mollusks have high economic value and are main circulation form in China currently.Tidal clam and deep sea scallop due to different habitats,have differences in storage characteristics of live products after capture.Seven species of bivalve molluscs were selected,the main economic species of the Da Lian,including clam?ruditapes philippinarum,mactraveneriformis,mactra chinenesis,saxidomus purpuratus?,scallop?patinopecten yessoensis?,ark shell?scapharcasubcrenata?,ablone?haliotis discus hannailno?,conch?rapana vanosa?,and octopus?octopus variabilis?.Based on the exploration of the raw material characteristics of the edible parts,the protein distribution patterns of different species and different types of muscles were analyzed.Beside,The physicochemical properties of myofibrillar protein and the effect of paramyosin on muscle contraction were analyzed.We were aiming at provide basic information for the change mechanism of live product.First,approximate composition of edible parts data showed that all meterial exhibited high protein and low fat characteristics,crude protein ranged from 60%to 82%,crude fat was below4.0%.Muscle protein amino acid composition of each species were investigated.Results showed that,there were 17 amino acids in all species,and the content of leucine?1.13¹.58 g/100g?and lysine?1.12¹.62 g/100g?were higher than other essential amino acids.Alanine,aspartic acid,glycine and glutamic acid were higher than other non-essential amino acids,glutamic acid was the highest,ranging from 2.46 to 3.35 g/100 g.Then muscle protein components were analyzed using SDS-PAGE.Common protein compo-nents were observed,including myosin,paramyosin,actin and tropomyosin.However,unknown aggregates which molecular weight more than 200kDa were found except scallop?Patinopecten yessoensis?,ark shell?scapharca subcrenata?and octopus?octopus variabilis?.Mass spectrometric were conducted to identify the unknown aggregate.Analysis result showed it was an aggregate paramyosin.In summary,the muscle paramyosin distribution was a main distinguished index for different species.Further,to explore the protein distribution and physicochemical properties differences between striated?ST?and smooth?SM?muscle of Patinopecten yessoensis.It was found that the striated muscle fibers were thicker and denser than smooth muscle.Myorod only existed in smooth muscle.The content of paramyosin in smooth muscle was 31%,however,it was only 11%in striated muscle.The smooth muscle solubility was characterized by S-shaped curve,which different from striated muscle showed a linear rise in the range of 0.05¹.0 mol/L salt concentrati-on.Beside,ATP content was 1.94?mol/g in smooth muscle and 5.18?mol/g in striated muscle.Myosin solubility increased with exogenous ATP concentrations increasing.The two muscles had different ATP-decomposing abilities.Compared with their optimal temperature conditions,Mf Ca²⁺-ATPase activity in striated muscle was approximately 10 times that of smooth muscle.Finally,to explore the effect of paramyosin on myosin Ca²⁺-ATPase activities.No correlation was detected between the ratio of paramyosin and Ca²⁺-ATPase activity of each meterial.There was no significant difference in Ca²⁺-ATPase activity at the ratio of myosin and paramyosin was 1:1,1:1.5,1:3.Result indicated that there was no significant interaction between myosin and myosin?myosin 0-0.6 mg/mL,paramyosin 0-1.8 mg/mL?.Further,the mechanism of intramolecular aggregation of paramyosin was explored.Ionic strength and alkaline phosphatase had no effect on depolymerization of aggregated paramyosin mercaptoethanol also failed to open the two subunit structures of the aggregate.The mechanism and properties of aggregated paramyosin formation have to be further studied.