Structure proteins muscle, extractability

Most of the machinery of living cells is made of enzymes. Thousands of them have been extracted from cells and have been purified and crystallized. Many others are recognized only by their catalytic action and have not yet been isolated in pure form. Most enzymes are soluble globular proteins but an increasing number of RNA molecules are also being recognized as enzymes. Many structural proteins of the cell also act as catalysts. For example, the muscle proteins actin and myosin together catalyze the hydrolysis of ATP and link the hydrolysis to movement (Chapter 19). Catalysis is one of the most fundamental characteristics of life. 

The analyses carried out up to now on such extracts have been based upon differences of solubility (see p. 235). The discussion of the results obtained has made clear that a reinvestigation of these mixtures is necessary in order to define more accurately the structure proteins of fish muscle. Electrophoresis, which permits the analysis of such mixtures with a minimum of alteration, appears a particularly suitable method. It has been applied as yet only to carp muscle extracts of high ionic strength (Hamoir, 1951b, 1954, 1955). In view of the very constant electrochemical behavior of the muscle structure proteins (see Hamoir, 1953a), it seems safe to assume that similar results will be obtained with other fishes. The results already obtained will therefore be more extensively described. The slight difference in extractibility previously mentioned between white and red rabbit muscles (Crepax, 1952) suggests that a separate study of both fish muscles would also be desirable in this case, but it has not yet been undertaken. 

The various structural proteins of Fig. 11 and 12 may thus be isolated. Their behavior is very similar to the corresponding components of rabbit muscle, but their extractibility is quite different. Fish actomyosin goes easily into solution and rabbit actomyosin dissolves with difficulty. Fish tropomyosin can be selectively extracted at fi 1 and pH 5.2, whereas similar experiments on rabbit muscle reveal only a very small solubilization of this protein (Van de Bergh, unpublished results). Fish muscle is fundamentally similar to other striated muscles but seems to be characterized by a looser association of its structure components. 

Electron Microscopy. Examination of fish proteins by electron microscopy conclusively shows that actomyosin aggregates during frozen storage (59,63,69). The change in structures of the extracted myofibrillar proteins and of the myofibril residues of frozen-stored cod muscle was studied by electron microscopy. The decrease in the number of actomyosin filaments and an increase in the number and size of large aggregate were found (69). Unfrozen carp actomyosin, either dissolved in 0.6M KC1 or suspended in 0.05M KC1, exists in a typical arrowhead... 

Actin is generally obtained from acetone-dried muscle powder by extraction with either water or, provided ATP is present, with KI solutions. Under these conditions the globular form of the protein is obtained, which polymerizes to the fibrillar form in 0.1 M KCl containing traces of Mg++ or Ca++ ions. Fibrillar actm combines with myosin to give actomyosin. Nevertheless, the exact structure and mode of action of the actomyosin complex are still far from being fully understood. 

It thus seems true to say that the extractability of L-myosin and actin depends solely on the mutual combination of these proteins, and the hindrance to diffusion by the surrounding muscle structures (cf. Dubuisson, 1947). 

Paramyosin has not yet been extracted in the usual sense. It is obtained from certain mollusc muscles by grinding in Edsall-Weber solution, destroying the gross structure, and bringing much of the protein into solution. In such extracts the paramyosin occurs in the form of intact fibrils, which dissolve at ionic strength 0.6 (Schmitt et al, 1947). 

This review focuses on the extraction of lipids from plant and muscle tissues using supercritical CO2 with an emphasis on the effect of structural and compositional differences as well as C02/lipid/protein/water interactions. The effect of moisture content ranging from 3-20% in oilseeds to 3-64% in muscle tissues on hpid and water extractability and residual proteins is demonstrated. 

Extraction kinetics of lipids and mass transfer resistance depend in part on the cell and tissue structures of the feed material as well as the interactions between C02/lipid/water/protein. Differences in the structure of plant and muscle tissues and the location of lipids within the tissue result in different extraction kinetics. In addition, the... 

Suiimi is a concentrate of insoluble muscle proteins (ca. 20%). It forms a solid cohesive gel with water (ca. 80%), which solidifies when warm For production, lean fish meat is ground at 5-10 °C and extracted with water until basically only myosin, actin, actomyosin and small amounts of collagen remain. The addition of paramyosin (cf. 13.1.4.2.2) intensifies the structure of the gel. In the further processing of Surimi to Kamboko, starch (ca. 5%), egg white, flavor enhancers, colorants and aroma substances are added, whereby an attempt is made to imitate crab or mussel meat. The resulting mixture is solidified by denaturation of the proteins first at 40-50 °C and then at 80-90 °C. Fibrous structures are produced by extrusion. 

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