Research On The Difference Proteomics Of Two Kinds Of Ocean Tuna

Tuna is delicious and nutritious, which has been loved by people. With the growing maturity of its fishing and processing technology, tuna has become an important marine food. Yellowfin(Thunnus albacores) and Albacore(Thunnus alalunga) tuna are two typical oceanic tuna and have many similarities. However, Albacore is rarer, more nutritious and expensive than Yellowfin. Thus dealer often use Yellowfin instead of Albacore to gain high profits. So a method which can distinguish their identification is very necessary. In this paper, back muscle of Yellowfin and Albacore was used as experimental material for the study and research. First nutrients of muscle of two tuna were analyzed and evaluated; then the fish protein was separated into different types. The content of different proteins and their relevant characteristics were measured. Use TEM to observe the microstructure of their musule; next two-dimensional electrophoresis gel technology was used to separate proteins furtherly; finally the typical differentially expressed protein spots were identified by mass spectrometry. The main results were as followed:1. The back muscle of two tuna had higher protein content and a reasonable amino acids ratio. Essential amino acids and Essential Amino Acids Index (EAAI) of Yellowfin was 40.70% and 92.62, Albacore was 41.70% and 95.00. This indicated that the nutritional value of amino acids from Albacore was better than Yellowfin. Besides the back muscle of two tuna had higher content of polyunsaturated fatty acids, especially DHA and EPA.The content of Yellowfin was 28.84% and 6.28%, while the content of Albacore was 29.83% and 7.43%. In addition, the back muscle of two tuna was also rich in mineral elements. They were health food products. To sum up, the nutritional value of back muscle of Albacore was better than Yellowfin.2. The protein compositions of two tuna were significantly different except the water-soluble protein. The content of salt-soluble protein in Yellowfin was 40.35% higher than 31.32% in Albacore, while other proteins are less than Albacore. According to polyacrylamide gel electrophoresis (SDS-PAGE) result, the molecular weight distribution was, at some level, different between Yellowfin and Albacore. Then the actomyosin of two kinds of tuna was extractcated and its Ca2+ -ATP enzyme activity, total and active thiol molar concentrations were determined. The result showed that the actomyosin of Yellowfin was more active than Albacore. Further more, the microstructure difference of two tuna was found by TEM. Found that Myofibril of Yellowfin was more compact than albacore. So the muscle of Yellowfin was also tighter than albacore.3. The protein of Albacore and Yellowfin were futher separated by two-dimensional electrophoresis technique to gain high resolution and reproducible protein profiles. Gel patterns were analysied by Image Master 2D software. The results showed that the match rate of gel patterns of two tuna (n=3) were all above 79%(P<0.05). More than 1700 protein points were obtained from all the gel patterns. A comparative analysis of two tuna maps showed that different proteins between Yellowfin and Albacore were 279 points (P<0.05), of which 62 spots was the species-specific proteins.4.18 protein spots which can represent the difference of two tuna and were statistical were identified by mass spectrometry.12 protein spots were successfully identified. The identification success rate was 66.7%. Three of them were homologous proteins. So 8 differentially expressed proteins which can distinguish between Yellowfin and Albacore were identified. They were Skeletal myosin heavy chain (Thunnus thynnus), Myosin heavy chain-1 (Thunnus orientalis), Myosin heavy chain-2 (Thunnus orientalis), Myosin light chain 2(Thunnus thynnus),14-3-3 protein gamma (Thunnus orientalis), Beta-actin (Thunnus maccoyii), Bile salt-activated lipase 1 (Thunnus thynnus) and Myostatin (Euthynnus alletteratus).In this paper, the nutrients and protein characteristics of Yellowfin and Albacore were tested. Their differential proteins were found and indentified by proteomic method to establish a method of determining the Yellowfin and albacore speciesit. It laid the foundation for species identification of tuna and its further processing and utilization.