Tissue distribution, inhibition and activation of gelatinolytic activities in Atlantic cod (Gadus morhua)

Identification of a Tissue Inhibitor of Metalloproteinase-2: An Endogenous Inhibitor of Modori-Inducing Insoluble Metalloproteinase from Yellowtail Seriola quinqueradiata Muscle

The existence of an endogenous protease inhibitor (EPI) was expected from the comparison of the gel properties between washed and nonwashed yellowtail surimi gels. A possible candidate, tissue inhibitor of metalloproteinase-2 (TIMP-2), was partially purified from the soluble fraction of yellowtail muscle, and an 18 kDa protein band was detected by sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) under nonreducing conditions and western blot analysis. Its N-terminal amino acid sequence was determined as XSXSPAHPQQAF, with high homology to TIMP-2 from other fish species, suggesting that it was identified as yellowtail TIMP-2. Subsequently, full-length cDNA of two isoforms (TIMP-2a and TIMP-2b) was successfully cloned from yellowtail muscle. The N-terminal sequence of purified TIMP-2 completely corresponded to TIMP-2b. When the surimi gel quality decreased after spawning, the mRNA expression of TIMP-2b also decreased. Human TIMP-2 could inhibit autolysis of myofibrillar proteins from yellowtail muscle. Thus, TIMP-2b was considered the major EPI of the modori-inducing insoluble metalloproteinase in yellowtail muscle.

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.

Compliance of the fish outflow tract is altered by thermal acclimation through connective tissue remodelling

To protect the gill capillaries from high systolic pulse pressure, the fish heart contains a compliant non-contractile chamber called the bulbus arteriosus which is part of the outflow tract (OFT) which extends from the ventricle to the ventral aorta. Thermal acclimation alters the form and function of the fish atria and ventricle to ensure appropriate cardiac output at different temperatures, but its impact on the OFT is unknown. Here we used ex vivo pressure-volume curves to demonstrate remodelling of passive stiffness in the rainbow trout (Oncorhynchus mykiss) bulbus arteriosus following more than eight weeks of thermal acclimation to 5, 10 and 18°C. We then combined novel, non-biased Fourier transform infrared spectroscopy with classic histological staining to show that changes in compliance were achieved by changes in tissue collagen-to-elastin ratio. In situ gelatin zymography and SDS-PAGE zymography revealed that collagen remodelling was underpinned, at least in part, by changes in activity and abundance of collagen degrading matrix metalloproteinases. Collectively, we provide the first indication of bulbus arteriosus thermal remodelling in a fish and suggest this remodelling ensures optimal blood flow and blood pressure in the OFT during temperature change.

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 metalloproteinases in fish biology and matrix turnover

Matrix metalloproteinases have important functions for tissue turnover in fish, with relevance both for the fish industry and molecular and cellular research on embryology, inflammation and tissue repair. These metalloproteinases have been studied in different fish types, subjected to both aquaculture and experimental conditions. This review highlights studies on these metalloproteinases in relation to both fish quality and health and further, the future importance of fish for basic research studies.

RESPONSE OF TRACHYDISCUS MINUTUS (XANTHOPHYCEAE) TO TEMPERATURE AND LIGHT(1)

The effects of different temperatures and light intensities on growth, pigments, sugars, lipids, and proteins, as well as on some antioxidant and proteolytic enzymes of Trachydiscus minutus (Bourr.) H. Ettl, were investigated. The optimum growth temperature and light intensity were 25°C and 2 × 132 μmol photons · m(-2 ) · s(-1) , respectively. Under these conditions, proteins were the main biomass components (33.45% dry weight [dwt]), with high levels of carbohydrates (29% dwt) and lipids (21.77% dwt). T. minutus tolerated temperatures between 20°C and 32°C, with only moderate changes in cell growth and biochemical composition. Extremely low (15°C) and high (40°C) temperatures decreased chl and RUBISCO contents and inhibited cell growth. The biochemical response of the alga to both unfavorable conditions was an increase in lipid content (up to 35.19% dwt) and a decrease in carbohydrates (down to 13.64% dwt) with much less of a change in total protein content (in the range of 30.51%-38.13% dwt). At the same time, the defense system of T. minutus was regulated differently in response to heat or cold treatments. Generally, at 40°C, the activities of superoxide dismutase (SOD), catalase (CAT), and proteases were drastically elevated, and three polypeptides were overexpressed, whereas the glutathione reductase (GR) and peroxidase (POD) activities were reduced. In contrast, at 15°C, all these enzymes except GR were suppressed. The effect of light was to enhance or decrease the temperature stress responses, depending on intensity. Our studies demonstrate the broad temperature adaptability of T. minutus as well as the potential for the production of valuable algal biomass.

Purification and characterization of a gelatinolytic metalloproteinase from the skeletal muscle of red sea bream (Pagrus major)

A gelatinolytic metalloproteinase (gMP) from red sea bream ( Pagrus major ) skeletal muscle was highly purified by ammonium sulfate fractionation and column chromatographies including (diethylamino)ethyl (DEAE)-Sephacel, phenyl-Sepharose, and gelatin-Sepharose. Purified gMP revealed two bands with molecular masses of 52 and 55 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing conditions. The 55 kDa band is quite possibly a glycosylated form of the 52 kDa band. The proteinase revealed optimal activity at 40 degrees C and pH 8.0. Metalloproteinase inhibitors including ethylenediaminetetraacetic acid (EDTA), ethylene glycol bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), and 1,10-phenanthroline specifically suppressed its activity. gMP was also significantly inhibited by cysteine and dithiothreitol. Divalent metal ion Ca(2+) is essential for its gelatinolytic activity. Thus, the proteinase is regarded as a matrix metalloproteinase-like proteinase. Furthermore, gMP hydrolyzed gelatin and type-I collagen effectively even at 4 degrees C, suggesting the possibility of its involvement in the texture tenderization of fish muscle during the post-mortem stage.

Matrix metalloproteinases are less essential for the in-situ gelatinolytic activity in heart muscle than in skeletal muscle

In order to determine whether the contribution of matrix metalloproteinases (MMPs) to the tissue gelatinolytic activity is similar between myocardium and skeletal muscle tissue, in-situ zymography was applied to myoblasts originated from myocardium or skeletal muscle of rodents as well as tissue sections of heart and soleus muscles of rats. Gelatinolyic activity was observed in cytoplasm and nucleus of both heart and skeletal myoblasts. The chelating agent EDTA blocked much of the gelatinolytic activity and the organomercurial activator of MMPs increased the activity in cells of both muscle origins. However, the inhibition of gelatinolytic activity by a broad spectrum MMP inhibitor was less profound in heart myoblasts than that in skeletal myoblasts. Gelatinolytic activity was also expressed in the endomysium and perimysium of tissue sections of heart and soleus muscles. Similar with findings in the cell studies, the gelatinase activity was increased by the MMP activator, mostly blocked by EDTA and partially inhibited by the MMP inhibitor. In the presence of the MMP inhibitor, the remaining gelatinolytic activity in the tissue sections was again higher in myocardium than that in soleus muscle. This observation was further supported by the gelatinolytic activity examined in tissue homogenates. Our findings suggest that other proteinases, in addition to MMPs, are more responsive for the tissue gelatinolytic activity in heart muscle as compared with that in skeletal muscle.

Seminal plasma proteins of Atlantic halibut (Hippoglossus hippoglossus L.)

Protein content and properties in the seminal plasma of Atlantic halibut (Hippoglossus hippoglossus) were assayed using spectrophotometric and electrophoretic methods. The protein concentration ranged from 6.4 +/- 3.1 to 19.4 +/- 3.4 mg ml(-1) and anti-proteolytic activity from 585.2 +/- 104.6 to 2912.4 +/- 367.4 U l(-l). A high correlation between anti-proteolytic activity and protein concentration (r = 0.95), and between sperm concentration and osmolality was found (r = 0.92). There was a significant decrease in anti-proteolytic activity from the first to the second sampling, but not in protein concentration. Anti-proteolytic activity and protein concentration were significantly affected by variations in individual males. Electrophoresis revealed four anti-proteolytic bands and individual differences in bands of proteolytic activity, which were subsequently characterized as metalloproteases and serine proteases.

Expression profiles of matrix metalloproteinase 9 in teleost fish provide evidence for its active role in initiation and resolution of inflammation

Matrix metalloproteinase 9 (MMP-9) belongs to a family of zinc-dependent endopeptidases. As a consequence of its ability to cleave structural extracellular matrix molecules, mammalian MMP-9 is associated with vital inflammatory processes such as leucocyte migration and tissue remodelling and regeneration. Interestingly, MMP-9 genes have been identified in fish, but functional data are still limited and focus on the involvement of MMP-9 in embryonic development, reproduction and post-mortem tenderization. Here, we describe the involvement of MMP-9 in the innate immunity of carp. In carp, MMP-9 was most notably expressed in classical fish immune organs and in peritoneal and peripheral blood leucocytes, indicating a role of MMP-9 in immune responses. In our well-characterized zymosan-induced peritonitis model for carp, we analysed expression of the MMP-9 gene and the gelatinolytic levels of both pro- and activated forms of MMP-9. The biphasic profile of MMP-9 mRNA expression indicated involvement during the initial phase of inflammation and during the later phase of tissue remodelling. Also, in vitro stimulation of carp phagocytes with lipopolysaccharide or concanavalin A increased MMP-9 gene expression, with a peak at 24 hr. The increase of MMP-9 mRNA correlated with the peak of MMP-9 gelatinolytic level in culture supernatants. These results provide evidence for an evolutionarily conserved and relevant role of MMP-9 in the innate immune response.

Purification and characterization of gelatinase-like proteinases from the dark muscle of common carp (Cyprinus carpio)

Gelatinolytic proteinases from common carp dark muscle were purified by 30-60% ammonium sulfate fractionation and a combination of chromatographic steps including ion exchange on DEAE-Sephacel, gel filtration on Sephacryl S-200, ion exchange on High-Q, and affinity on gelatin-Sepharose. The molecular masses of these proteinases as estimated by SDS-PAGE were 75, 67, and 64 kDa under nonreducing conditions. The enzymes revealed high activity at a slightly alkaline pH range, and their activities were investigated using gelatin as substrate. Metalloproteinase inhibitors, EDTA, EGTA, and 1,10-phenanthroline, almost completely suppressed the gelatinolytic activity, whereas other proteinase inhibitors did not show any inhibitory effect. Divalent metal ion Ca (2+) is essential for the gelatinolytic activity. Furthermore, these gelatinolytic proteinases hydrolyze native type I collagen effectively even at 4 degrees C, strongly suggesting their involvement in the texture softening of fish muscle during the post-mortem stage.

Trends in Postmortem Aging in Fish: Understanding of Proteolysis and Disorganization of the Myofibrillar Structure

Postmortem tenderization is caused by enzymatic degradation of key structural proteins in myofibrils as well as in extracellular matrix, and of proteins involved in intermyofibrillar linkages and linkages between myofibrils and the sarcolemma. The function of these proteins is to maintain the structural integrity of myofibrils. Current data indicate that calpains and cathepsins may be responsible for degradation of these proteins. Other phenomena occurring in cells postmortem (pH drop, sarcoplasmic Ca2+ increase, osmotic pressure rise, oxidative processes) may act in synergy with proteases. Our understanding of the underlying mechanisms of muscle degradation should be improved for an accurate evaluation of the postmortem muscle changes and consequently of the fish quality.

Detection of TIMP-2-like protein in Atlantic cod (Gadus morhua) muscle using two-dimensional real-time reverse zymography

Matrix metalloproteinases (MMPs) have been proposed to participate in postmortem degradation of fish muscle connective tissues during storage. In the extracellular matrix (ECM) of mammals, a group of specific tissue inhibitors of metalloproteinases (TIMPs) contributes in regulating the MMPs present. However, little information exists on the presence of TIMPs in fish. In this paper, the presence of TIMPs in the muscle of Atlantic cod (Gadus morhua) was investigated using gelatin affinity chromatography, real-time reverse zymography (RTRZ) and mass spectrometry (MS). Using RTRZ inhibitory action against cod muscle, proteinases binding to gelatin were detected in the muscle. The inhibitor had similar molecular weight (21 kDa) as a human recombinant TIMP-2 used as a reference sample. Because isoforms of TIMP-2 homologues with similar molecular weight have been suggested in fish, a two-dimensional RTRZ (2D RTRZ) method was designed. The new method showed the existence of only one form with inhibitory action against cod muscle proteinases. Finally, de novo sequencing of two peptides derived from the cod muscle inhibitor showed high homology to TIMP-2s both from human and other teleosts.