title: Characterisation of proteolytic enzymes from muscle and hepatopancreas of fresh water prawn (Macrobrachium rosenbergii).
abstract: BACKGROUND
  Fresh water prawn in Thailand is widely consumed due to its delicacy. During postmortem handling and storage, prawn meat becomes soft and mushy, probably as a result of indigenous proteases. Therefore, an understanding of prawn proteases associated with the degradation of muscle proteins from fresh water prawn could pave the way for prevention of such a phenomenon during extended storage.
  
  
  RESULTS
  Proteolytic enzymes in the crude extract (CE) from muscle and hepatopancreas of fresh water prawn (Macrobrachium rosenbergii) were characterised. CE from muscle exhibited the highest hydrolytic activities towards haemoglobin at pH 5 and 50 °C, while that from hepatopancreas had the highest activity on casein at pH 7 and 60 °C. Based on inhibitor study, cysteine protease and serine protease were dominant in CE from muscle and hepatopancreas, respectively. CE from muscle rarely hydrolysed natural actomyosin (NAM), but could not degrade pepsin-soluble collagen (PSC). Conversely, NAM and PSC were susceptible to hydrolysis by CE from hepatopancreas as evidenced by the marked decreases in band intensity. Activity staining using haemoglobin, casein and gelatin as substrates revealed that no proteolytic or gelatinolytic activity was observed in CE from prawn muscle, while CE from hepatopancreas exhibited pronounced hydrolytic activities towards all substrates. CE from muscle showed calpain and cathepsin L activities but CE from hepatopancreas mainly exhibited tryptic and chymotryptic activities.
  
  
  CONCLUSIONS
  Serine proteases, mainly trypsin-like or chymotrypsin-like, from hepatopancreas were probably responsible for the softening of prawn meat during postmortem storage via the degradation of both muscle and connective tissues.
authors.affiliation: Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla, Thailand.
authors.forename: Chodsana
authors.initials: C
authors.lastname: Sriket
authors.forename: Soottawat
authors.initials: S
authors.lastname: Benjakul
authors.forename: Wonnop
authors.initials: W
authors.lastname: Visessanguan
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D002154:Calpain / Q000378:metabolism; D056668:Cathepsin L / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D005519:Food Preservation; D005780:Gelatin / Q000378:metabolism; D043143:Hepatopancreas / Q000201:enzymology*; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D033541:Palaemonidae / Q000201:enzymology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D017747:Seafood; D014357:Trypsin / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D005780:Gelatin; D003094:Collagen; D000205:Actomyosin; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D014357:Trypsin; D002154:Calpain; D056668:Cathepsin L