Fish proteins comparative

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

This implicated target site insensitivity is more effectively demonstrated when actual amounts of endrin present in brain tissue of Ss fish are compared to Ra fish (7). In Ss fish the endrin concentration in the forebrain is 24 ng endrin equiv-alents/mg protein while in the same brain fraction of Ra fish there was 1150 ng endrin equivalents/mg protein. Further, when the amount of endrin in various brain fractions from R fish exposed to 1500 yg/1 c-endrin is monitored with time, up to 4560 ng endrin equivalents/mg protein appears in the brain fractions of Ra fish after 24 hr endrin exposure (Table VI). 

Plasma binding - both the quantity and types of proteins in plasma differ in these classes of animals. Mammals tend to have large amounts of protein compared with fish (ca. 8 vs 3 g/100 ml) and albumin, the protein which binds most xenobiotics, is negligible in a number of fish species. 

The circulatory system of fish is also unique structurally and functionally. Structurally, the membranous nature of the vasculature makes for a friable high-capacitance system under low pressure. Low blood flows result in somewhat longer distributional phases for many drugs. Processes such as heart rate and stroke volume that influence drug distribution are themselves influenced by external factors such as temperature and stress. In addition, total plasma protein content differs in fish as compared to mammals. Total plasma protein in the trout and flounder is approximately one-half that of mammals such as dogs and cats. For many compounds protein binding is considerably lower in fish than their mammalian counterparts (19, 20). 

Bergeron, N., and Jacques, H. 1989. Influence of fish protein as compared to casein and soy protein on serum and hver hpids, and serum lipoprotein cholesterol levels in the rabbit. Atherosclerosis, 78,113-121. 

The comparative biochemistry of proteins is still in its beginning. Research was first directed towards the study of the protein components of mammals, but is now extending to other classes of vertebrates. In the case of fish, this study, of great economic importance, has been contributed to both by protein chemistry and technology. The main characteristics of fish protein are now satisfactorily defined, and a comparison of the highest and lowest classes of vertebrates is possible from the point of view of protein composition. 

Table IV shows the effect of protein concentration on foam volume and stability compared with egg white and soy isolate. Foam volumes for the hydrolyzed, succinlyated fish protein were highest at 3 g protein/ 100 ml, but decreased at 4 g/100 ml. Compared with egg white and soy isolate, the hydrolyzed succinylated fish protein yielded a more stable, but less voluminous foam.

While several laboratories have shown that severe racemiza-tion of proteins can occur during treatment with sodium hydroxide (6,18,22-24,61,62) the effects of other alkalis used in food processing are documented less well. Jenkins, et al. (70) have observed substantial differences in the degree of racemization caused by lime or caustic soda treatment of zein. Lime causes only 50% to 90% of the racemization observed for several amino acyl residues compared to when caustic soda is used. Because a substantial amount of calcium ion remained bound to the protein (approx. 10,000 ppm) compared to l/20th that amount of sodium ion for the caustic soda-treated zein, it is possible that divalent calcium may stabilize the protein making it less susceptible to racemization. Tovar (14) observed increases of 40% to 50% in serine and phenylalanine racemization and a decrease of 30% aspartate racemization for caustic soda-treated fish protein concentrate compared to lime-treated protein (see Table II). These studies indicate that different alkalis have different effects on racemization of proteins specifically, lime may cause less racemization than caustic soda at a similar pH. 

Cytochrome c derived from tuna fish reacts slower with the immobilized oxidase compared to cytochrome c derived from horse at the same concentration. This is due to a smaller protein/enzyme dissociation constant for tuna protein compared to horse protein. These data show that electron transfer from tuna cytochrome c to the enzyme is rate limiting even at concentrations of 10 xM and above. 

The protein-N content of fish muscle tissue is between 2-3%. The amino acid composition, when compared to that of beef or milk casein (Table 13.6), reveals the high nutritional value of fish proteins. The sarcoplasma protein accounts for 20-30% of the muscle tissue total protein. The contractile apparatus accounts for 65-75% protein the connective tissue of teleosts is 3% and of elasmobranchs, such as sharks and rays (skate or rocker), is up to 10%. The individual protein groups and their functions in muscle tissue of mammals (cf. 12.3.2) also apply to fish. 

Watanabe and Arai wrote an excellent review on the properties of enzymatically modified proteins and compared the chemical and enzymatic processes of various proteins [135]. Enzymatic processes can normally be carried out under milder and therefore safer experimental conditions than conventional chemical processes. Proteolytic enzymes have been used on proteins to improve their solubility soy protein, leaf protein concentrates, fish protein concentrates, meat proteins, egg proteins, milk proteins, and blood proteins. Special attention was given to caseins, gelatins, egg proteins, and cereals. Partial hydrolysis of these proteins under well-controlled conditions can produce emulsifying and whipping agents... 

Algae can be cultivated easily and quickly when compared to plants. They produce very high quantities of carotenoids compared to other sources (3.0 to 5.0% w/w on a dry weight basis). They contain both cis and trans isomers of carotenoids for high bioavailability and bioefflcacy, and also contain oxygenated carotenoids (xantho-phylls), which have greater bioactivity and better anticancer properties. The proteins from Dunaliella biomass can be utilized for bread and other products and whole cells can be utilized for animal, poultry, and fish foods because they are safe. ... 

This area was the most profusely studied in the AQUATERRA project in terms of biological effects in fish populations. Barbel and bleak were the sentinel species selected in this area and an array of histological and biochemical tests were used to monitor the impact due to three major sources of pollution mercury and OCs at Monzon (with a comparison in one of the papers with Flix) and PBDEs in Barbastro [1—4, 37]. Mercury pollution was directly correlated to an increase of MTprotein in the liver of barbel captured downstream Monzon when compared to samples captured upstream (Fig. 3a). However, mRNA quantitative analyses failed to show any differences between downstream and upstream Monzon, neither correlated with MT protein levels. Further studies showed that MT mRNA in liver is a rather weak marker for chronic metal pollution in liver (see below) [4], The presence of degenerative hepatocytes in barbels and bleaks was also linked to mercury poisoning although it can also reflect the impact by other pollutants, like OCs or PBDEs (Fig. 3e). 

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