Proteins fish muscle

Great amount of marine fish species have been identified with potential nutraceutical and medicinal values. Consequently, a number of bioactive compounds have been identified including fish muscle proteins, peptides, collagen and gelatin, fish oil, fish bone. Bioactive peptides derived from various fish muscle proteins have shown various biological activities including antihypertensive, antibacterial, anticoagulant, anti-inflammatory, and antioxidant activities, and hence they may be a potential material for biomedical and... 

Discarded fish bones and cutoffs may contain considerable amounts of muscle proteins. These muscle proteins are nutritionally valuable and easily digestible with well-balanced amino acid composition (Venugopal et al., 1996). Therefore, fish proteins derived from seafood processing by-products can be hydrolyzed enzymatically to recover protein. Protein hydrolysates from several marine species have been analyzed for their nutritional and functional properties, and researches have mainly explored the possibility of obtaining biologically active peptides (Benkajul and Morrissey, 1997). Moreover, skipjack tuna muscle (Kohama et al., 1988), sardine muscle (Bougatef et al., 2008), and shark meat (Wu et al., 2008) have been used to separate potential peptides. 

In contrast to milk, where samples are primarily derived from cows, meat analysis has to be performed in samples of a widely different animal origin including cattle, lamb, swine, poultry, and fish. Muscle is a complex matrix with a pH of 5.7, composed of muscle fibers, various types of connective tissue, adipose tissue, cartilage, and bones. Sarcoplasmic proteins such as myoglobin, and glycolytic enzymes are soluble in water while the myofibrillar proteins such as myosin and actin are soluble in concentrated salt solutions (14). The connective tissue proteins, collagen and elastin, are insoluble in both solvents. 

Figure B3.1.1 A 15% SDS-polyacrylamide gel stained with Coomassie brilliant blue. Protein samples were assayed for the purification of a proteinase, cathepsin L, from fish muscle according to the method of Seymour et al. (1994). Lane 1, purified cathepsin L after butyl-Sepharose chromatography. Lane 2, cathepsin L complex with a cystatin-like proteinase inhibitor after butyl-Sepharose chromatography. Lane 3, sarcoplasmic fish muscle extract after heat treatment and ammonium sulfate precipitation. Lane 4, sarcoplasmic fish muscle extract. Lanes M, low-molecular-weight standards aprotinin (Mr 6,500), a-lactalbumin (Mr 14,200), trypsin inhibitor (Mr 20,000), trypsinogen (Mr 24,000), carbonic anhydrase (Mr 29,000), gylceraldehyde-3-phosphate dehydrogenase (Mr 36,000), ovalbumin (Mr 45,000), and albumin (Mr 66,000) in order shown from bottom of gel. Lane 1 contains 4 pg protein lanes 2 to 4 each contain 7 pg protein.

Fig. 13. Illustrations of the possible arrangement of C-protein (MyBP-C) on the myosin filament backbone in projection down the axis (A) and in axial view (B). Of particular importance here is the possibility that the N-terminal half of C-protein extends out and binds to actin in relaxed muscle. (C) Simulation of the possible interactions of C-protein with binding sites on actin generated using the program MusLABEL (Squire and Knupp, 2004). (D) Left left half of the low-angle X-ray diffraction pattern from bony fish muscle (as in Fig. 11C), showing (right) the possible positions where the C-protein array in (D) might contribute. (From Squire elal, 2003d.)...

Fig. 14. Model of the A-band filament lattice in bony fish muscle, based on Hudson et al. (1997) and Squire et al. (2003d), showing the central myosin filament with its projecting myosin heads, together with C-protein in orange and actin filaments colored as in Fig. 11A and B.

Muravskaya, 1978 Diana and Mackay, 1979 Shatunovsky, 1980). However, in all starved fish it is the lipid that is mobilized first, except possibly in the eel. In fatty fish, much lipid is used from the flesh, while in lean fish it is used from the liver. In both types of fish, muscle protein is mobilized only when the lipid resources fall below a critical level. Black and Love (1986) showed that energy substrates are mobilized in a definite sequence, white muscle protein, for example, being metabolized at an earlier stage than red muscle protein, while, on refeeding, the latter is replenished before the former. 

Dambergs, N. (1963). Extractives of fish muscle. 3. Amounts, sectional distribution and variations of fat, water-solubles, protein and moisture in cod fillets. Journal of the Fisheries Research Board of Canada 20,909-918. 

Lipid oxidation products react with proteins and other amino compounds to form brown substances, similar to melanoidins. The formation of such brown substances was reviewed already at the first Maillard Symposium.150 The pigments formed are partly soluble in chloroform-methanol and partly insoluble, whereas true melanoidins are largely water-soluble. As most brown pigments of fish muscle are soluble in benzene-methanol and only to a lesser extent in water, the implication is that here oxidised lipid-protein interactions are more important than Maillard browning due to ribose-amino acid interactions. 

In recent years several applications of the HC1 proteolysis have been published in the field of Se speciation, for example, as regards Se-enriched lactic acid bacteria [66], mullet and cockles [8], and algae [67], where the technique provided extraction efficiencies of greater than 90 percent and preserved the integrity of the selenoamino acids. The general usefulness of this method of Se speciation is, however, questionable. Sometimes the authors do not state clearly whether phenol - an essential compound for the prevention of oxidation of SeCys - was used or not. In practice, neither phenol nor the short-duration MW-assisted irradiation can prevent the alteration of selenoamino acids [68-71], At the moment, no final conclusion on the applicability of HC1 proteolysis can be drawn, as CRMs certified for SeCys are still unavailable. On the other hand, an Se extraction efficiency of 80-90 percent can be achieved with this method only if either proteins are at least partly separated from the other components of the matrix, for example, separate analysis of fish muscles is carried out [8], or a considerable portion of Se is originally contained in inorganic forms in the sample, as observed by B Hymer and Caruso [1] in the case of Se-enriched food supplements. 

Most of the studies indicate that denaturation of muscle proteins plays the dominant role in the quality changes of the frozen stored meats. The muscle proteins of fish and other aquatic animals have been found to be much less stable than those of beef animals, pigs and poultry (1 ). The present paper will be limited primarily to fish muscle as one representative of vertebrate muscle and it will also deal primarily with the behavior of fish proteins at sub-zero temperatures. In order to do a thorough analysis within the space limit permitted, focus will be on the changes of the proteins per se leaving peripheral problems to other reviews (2-18). 

Chemical constitution. The approximate composition of mammalian muscle is 16-22% protein 1.5-13% lipid 0.5-13% carbohydrate 1% inorganic matter and 65-80% water (21). Poultry muscle contains less lipid. The composition of fish muscles is 15-24% protein 0.1-22% lipid 1-3% carbohydrate 0.8-2% inorganic matter and 66-84% water (21-23). 

The amount of stroma proteins is less in fish muscles (3-5%) than it is In beef or rabbit muscles (15-18%). This may explain why raw fish fillets are acceptable in Japanese dishes, whereas beef, rabbit and pork are rarely served raw. According to Fennema et al. (9.), tenderness is primarily related to collagen content, while toughness and water-holding capacity are associated with the myofibrillar proteins. Many papers on cooked meat mention both tenderness and toughness, while those on cooked fish note the problems of toughness rather than tenderness. This also might be related to the difference in content of the stroma proteins. 

Actomyosin. At high salt concentrations ( . . 0.6 M KC1), actin and myosin combine to form actomyosin filaments giving a highly viscous solution. Actomyosin retains the ATPase activity of myosin and demonstrates "super-precipitation" on the addition of ATP (24,34). As expected, there are differences between actomyosins of rabbit and fish with respect to solubility (10,22,35,36), viscosity (46) and ultracentrifugal behavior (477. Since actomyosin is the most readily available form of myofibrillar proteins from fish muscle, its behavior relative to deterioration during frozen storage has been most frequently studied. 

Cryoprotectants which have so far been found to be effective for fish muscle proteins include such compounds as monosaccharides, oligosaccharides, polysaccharides of relatively small molecular size, di- and polyalcohols, hydroxymonocarboxylic acids, di- and tricarboxylic acids, acidic, basic and some other amino acids, and phosphates and their derivatives (15,16,66,67,72-74, 82,83,93,97-99,112-114,122,140-154). Dimethyl sulfoxide (DMSOT, which is cryoprotective for various biological materials such as red cells, was not effective for fish muscle proteins (147). 

Noguchi, S. In "Proteins of Fish Muscle" (Japanese Society of Scientific Fisheries, Ed.), Koseisha-Koseikaku K.K. Tokyo, 1977, 99. 

Methylmercury is rapidly and nearly completely absorbed from the gastrointestinal tract 90-100% absorption is estimated. Methylmercury is somewhat lipophilic, allowing it to pass through lipid membranes of cells and facilitating its distribution to all tissues, and it binds readily to proteins. Methylmercury binds to amino acids in fish muscle tissue. The highest methylmercury levels in humans generally are found in the kidneys. Methylmercury in the body is considered to be relatively stable and is only slowly transformed to other forms of mercury. Methylmercury readily crosses the placental and blood/brain barriers. Its estimated half-life in the human body ranges from 44 to 80 days. Excretion of methylmercury is via the feces, urine, and breast milk. Methylmercury is also distributed to human hair and to the fur and feathers of wildlife measurement of mercury in hair and these other tissues has served as a useful biomonitor of contamination levels. 

Regarding the bioavailability of methylmercury in fish, the available data indicate that methylmercury uptake is not affected by its presence in fish. Experimental studies on the metabolism of methylmercury in humans following the ingestion of contaminated fish (using methylmercury bound to fish muscle protein) have shown that absorption is almost complete (95% absorbed) (Miettinen 1973). Animal studies also support this absorption value. Data on cats given fish homogenates indicate absorptions of 90% of methylmercury, whether added to the homogenate, accumulated by fish in vivo, or from methyl-... 

Miettinen JK, Rahola T, Hattula T, et al. 1969. Retention and excretion of 203Hg- labelled methylmercury in man after oral administration of CH3203Hg biologically incorporated into fish muscle protein - preliminary results. Fifth RIS (Radioactivity in Scandinavia) Symposium, Department of Radiochemistry, University of Helsinki, Stencils, as cited in Berglund et al. 1971. 

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