Purification and characterization of a collagenolytic serine proteinase from the skeletal muscle of red sea bream (Pagrus major)

A comprehensive review of the control and utilization of aquatic animal products by autolysis-based processes: Mechanism, process, factors, and application

Animal aquatic products have high water content, abundant enzyme system and their own diverse microbial flora. These products are severely susceptible to autolysis and degradation after death, resulting in many adverse effects on storage, processing, and transportation. Among them, the endogenous enzyme are the key factor that caused the autolysis and degradation. Autolytic hydrolysis provides an effective way to maximize the use of aquatic by-products and achieve increased protein resources and reduce environmental pollution from by-products. To better acquaintance the autolysis phenomenon and regulation of the autolysis phenomenon. This paper reviews the autolytic mechanism, biochemical changes, influencing factors, and potential applications of animal aquatic products and their by-products to explore autolysis and its effective utilization and regulation. In addition, this study also emphasizes the importance of making full use of aquatic by-products. Furthermore, the research trends and future challenges of autolysis are also discussed. Autolysis can effectively transform aquatic products and by-products into bioactive hydrolysates. The hydrolysates produced by the autolysis of aquatic products and their by-products have attracted attention because of their wide applications in food, healthcare, and animal feed industries. However, the mechanism and regulation (promotion or inhibition) of autolysis should be further studied, and autolysate at the industrial level should be produced to provide high-value-added products for by-product processing and realize the sustainable utilization of resources.

Assessment of gelatinolytic proteinases in chilled grass carp (Ctenopharyngodon idellus) fillets: characterization and contribution to texture softening

BACKGROUND

Texture softening is always a problem during chilling of grass carp fillets. To solve this problem and provide for better quality of flesh, understanding the mechanism of softening is necessary. Gelatinolytic proteinases are suspected to play an essential role in the disintegration of collagen in softening of fish flesh. In the present study, the types and contribution of gelatinolytic proteinases in chilled fillets were investigated.

RESULTS

Four active bands (G1, 250 kDa; G2, 68 kDa; G3, 66 kDa; G4, 29 kDa) of gelatinolytic proteinases were identified in grass carp fillets by gelatin zymography. The effect of inhibitors and metal ions revealed that G1 was possibly a serine proteinase, G2 and G3 were calcium-dependent metalloproteinases and G4 was a cysteine proteinase. The effect of the inhibitors phenylmethanesulfonyl fluoride (PMSF), l-3-carboxy-trans-2,3-epoxy-propionyl-l-leucine-4-guanidinobutylamide (E-64) and 1,10-phenanthroline (Phen) on chilled fillets revealed that gelatinolytic proteinase activities were significantly suppressed. Collagen solubility indicated that metalloproteinase and serine proteinase played critical roles in collagen breakdown during the first 3 days, and cysteine proteinase revealed its effect after 3 days. Meanwhile, during chilled storage for 11 days, the final values of shear force increased 19.68% and 24.33% in PMSF and E-64 treatments when compared to control fillets respectively, whereas the increase after Phen treatment was 49.89%.

CONCLUSION

Our study concluded that the disintegration of collagen in post-mortem softening of grass carp fillets was mainly mediated by metalloproteinase and to a lesser extent by serine proteinase and cysteine proteinase. © 2021 Society of Chemical Industry.

Inhibition of post-mortem fish muscle softening and degradation using legume seed proteinase inhibitors

Inhibitors that control muscle softening are important for regulating the activities of specific proteinases in meat. Proteolytic activity of endogenous proteinases in postmortem fish leads to the deterioration of myofibres. Calpain proteolytic enzyme system in skeletal muscles is mainly responsible for the post-mortem proteolysis. Soluble sarcoplasmic serine proteinase and the insoluble myofibrillar serine proteinase fractions contribute to the modori effects in surimi gels while myosin heavy chains contribute to gel strength. Proteolytic degenerative processes negatively affect the entire quality spectrum of the fish as food. Legume seeds are a good source of proteinase inhibitors with the potential to emerge as a promising tool in fish meat quality management. Many workers have studied the potent inhibitory effect of the seed flour from various legume crops on the flesh, surimi gels and visceral proteinases of fishes. The present review provides collective information about proteolysis in fish and its control by using legume seed flour as a natural source of proteinase inhibitors. Use of legume seed flour can reduce the dependence of the meat processing industry on the non-renewable synthetic chemical agents. Moreover, the use of natural products from sustainable resources also leads to the improved economics of meat production.

Tissue inhibitor of metalloproteinase-2 (TIMP-2) from red seabream (Pagrus major): Molecular cloning and biochemical characterization of highly expressed recombinant protein

The tissue inhibitor of metalloproteinase-2 (TIMP-2) is originally characterized as an endogenous inhibitor of matrix metalloproteinases (MMPs) to response collagenolysis associated with immune challenge. In this study, the cDNA encoding TIMP-2a gene from red seabream (Pagrus major) muscle was cloned. It was 585 bp encoding a putative protein of 194 amino acids, which comprised all recognized functional domains and showed the high identity to TIMP-2as from other teleost fishes, revealing it belongs to TIMP-2a family. Soluble rTIMP-2a was efficiently expressed using a new constructed pPIC9K-rTIMP-2a vector with high inhibitory activity against to MMP-2 and MMP-9. The recombinant TIMP-2a tagged with 6 histidine residues showed the molecular mass of 23 kDa and isoelectric point of 6.50. Furthermore, the 6 disulfide bonds formed by 12 conserved cysteine residues were identified as functional motifs for its structural stability. In addition, rTIMP-2a possessed the high inhibitory activity against gelatinolytic hydrolysis and degradation of type I collagen which induced by endogenous MMPs in muscle. The results revealed the properties and inhibitory function of rTIMP-2a, which may be a pivotal role in regulation gelatinolytic MMPs metabolization during defense mechanism.

The enzyme profiles in the connective tissue attaching pin bones to the surrounding tissue is specific in farmed salmon (Salmo salar) and cod (Gadus morhua L.)

Post mortem storage is a necessary process for removal of pin bones without destruction of fillets, thereby avoiding volume and economic loss. However, the enzymes involved in loosening pin bones during storage have not been studied to a great extent. In this study, the activities and localization of MMPs in the connective tissue (CT) of pin bones dissected from fillet of salmon and cod were investigated. Interestingly, the enzyme activity profile in these two species was different during post mortem storage of fish fillets. Adding MMP inhibitor (GM6001) and serine protease inhibitor (Pefabloc) revealed different effects in the two species, suggesting different regulations in salmon and cod. In situ zymography with the same inhibitors verified MMP and serine protease activity in CT close to pin bone at early post mortem (6 h) in salmon. However, MMP inhibition was not evident in cod in this area at that time point. Immunohistochemistry further revealed MMP9 and MMP13 were located more to the outer rim of CT, facing the pin bone and adipose tissue, while MMP7 was more randomly distributed within CT in salmon. In contrast, all these three MMPs were randomly distributed in CT in cod. In summary, our study reveals different MMP enzyme profiles in salmon and cod in the pin bone area, influenced by serine proteases, and suggests that MMPs and serine proteases must be taken in consideration when studying the conditions for early pin bone removal.

Matrix Metalloproteinase 2 (MMP-2) Plays a Critical Role in the Softening of Common Carp Muscle during Chilled Storage by Degradation of Type I and V Collagens

Matrix metalloproteinases (MMPs) are proposed to play important roles in the degradation of collagens, thus causing the post-mortem softening of fish muscle, although the specific mechanism remains largely unresolved. Previously, we reported the existence of gelatinase-like proteinases in common carp (Cyprinus carpio) muscle. The primary structures of these proteinases, however, have never been investigated. In the present study, two MMPs with molecular masses of 66 and 65 kDa were purified to homogeneity from common carp muscle by ammonium sulfate fractionation and a series of column chromatographies. Matrix-assisted laser desorption/ionization-tandem time-of-flight mass spectrometry (MALDI-TOF/TOF-MS/MS) analysis indicated that they are completely identical to MMP-2 from common carp. During chilled storage of common carp at 4 °C, the enzymatic activity of MMP-2 increased to 212% in 12 h while the texture profile increased over the first 2 h and gradually decreased. On the other hand, type V collagen was purified to homogeneity and a specific polyclonal antibody against this protein was prepared. Both type I and V collagens were effectively hydrolyzed by MMP-2 at 30 °C and even at 4 °C. Furthermore, injection of metalloproteinase proteinase inhibitor EDTA into the blood vessel of live common carp suppressed post-mortem tenderization significantly. All of these results confirmed that MMP-2 is a major proteinase responsible for the degradation of collagens, resulting in the softening of fish muscle during chilled storage.

Characterisation of proteolytic enzymes from muscle and hepatopancreas of fresh water prawn (Macrobrachium rosenbergii)

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.

CONCLUSION

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.