title: Identification by GeLC-MS/MS of trypsin inhibitor in sarcoplasmic proteins of three tropical fish and characterization of their inhibitory properties.
abstract: Sarcoplasmic proteins from 3 fish species were fractionated by 50% to 70% ammonium sulfate precipitation. Lyophilized fractionated sarcoplasmic proteins of threadfin bream (TB-SP), bigeye snapper (BS-SP), and yellow croaker (YC-SP) showed 80% to 92% trypsin inhibitory activity. Trypsin inhibitory activity staining gel electrophoresis revealed bands at 32, 33, 37, 45, 48, and 50 kDa for the 3 species, and a band at 95 kDa was observed for TB-SP and YC-SP. Alpha-1-antitrypsin with molecular mass of 45 to 50 kDa was identified in YC-SP by gel-based liquid chromatography-tandem mass spectrometry (GeLC-MS/MS). Other major protein bands appeared on trypsin activity staining included phosphorylase, glyceraldehyde-3-phosphate dehydrogenase, and creatine kinase with molecular mass of 95 and 35 to 40 kDa, respectively. But, these 3 proteins did not show true trypsin inhibitory activity. Trypsin inhibitory activity of fractionated sarcoplasmic proteins showed good stability, with >80% activity retained at 60 °C and up to 0.6 M NaCl. TB-SP showed the highest inhibitory activity against autolysis of washed threadfin bream mince at 65 °C. Addition of 0.5% or 1% TB-SP improved textural properties of threadfin bream surimi gels preincubated at 37 or 65 °C followed by heating at 90 °C. Therefore, TB-SP could be a promising protein ingredient for enhancing surimi gel texture.
  
  
  CONCLUSIONS
  Threadfin bream, bigeye snapper, and yellow croaker are the main species used as raw material for tropical surimi production. Sarcoplasmic proteins from 3 species contain trypsin inhibitor(s) that can minimize proteolytic activity and improve gel texture of proteinase-laden fish muscle. Therefore, sarcoplasmic proteins that are byproducts from surimi processing of these species could be recovered, fractionated, and utilized as a functional protein ingredient.
authors: Food Protein Research Unit, School of Food Technology, Inst. of Agricultural Technology, Suranaree Univ. of Technology, Nakhon Ratchasima, 30000, Thailand.
authors: Siriphon
authors: S
authors: Siriangkanakun
authors: Eunice C Y
authors: EC
authors: Li-Chan
authors: Jirawat
authors: J
authors: Yongsawadigul
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid; D029941:Fish Proteins / Q000737:chemistry*; D005399:Fishes / Q000378:metabolism; D005782:Gels / Q000737:chemistry; D018995:Myosin Heavy Chains / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000737:chemistry*; D013045:Species Specificity; D053719:Tandem Mass Spectrometry; D014357:Trypsin / Q000378:metabolism; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029941:Fish Proteins; D005782:Gels; D014361:Trypsin Inhibitors; D014357:Trypsin; D018995:Myosin Heavy Chains
keywords: GeLC-MS/MS; sarcoplasmic proteins; surimi; tropical fish; trypsin inhibitor