Molecular Localization of Health-Promoting Peptides Derived from Fish Protein Hydrolyzates on Fish Muscle Proteins.

The four previously reported health-promoting dipeptides, valine-tyrosine, lysine-tryptophan, methionine-phenylalanine, and arginine-isoleucine, found in the fish muscle hydrolyzates, were mainly located in the myosin subfragment-1 heavy chain, whereas the health-promoting tripeptide, alanine-lysine-lysine, was found in the fibrous rod consisting of the myosin subfragment-2 and light meromyosin with a regular coiled-coil structure of α-helix, irrespective of the fish species. Furthermore, the localization of these peptides either in the random coil, β-sheet, or α-helix was also examined in the three-dimensional image, showing no specific tendency. Surprisingly, the same trend was observed even for the mammalian rabbit fast muscle myosin heavy chain.

Peptidomic Analysis of a Disintegrated Surimi Gel from Deep-Sea Bonefish .

Surimi gel is a commonly found gelled product in Japan. Disintegration of the surimi gel is mainly caused by proteolytic degradation of the myosin heavy chain (MHC) under an inappropriate heating process. Many studies have reported the decrease in MHC in the disintegrated surimi gel but the mechanistic details of this degradation remain unclear.

The effects of endogenous proteases within abdominal muscle parts on the rheological properties of thermally induced gels from white croaker (Pennahia argentata).

Three types of material meats were prepared from a so-called normal muscle part of white croaker (Pennahia argentata) containing 0, 4.2 and 8.4% of an abdominal muscle part.

Deterioration of white croaker (Pennahia argentata) meat thermally-induced gel products caused by proteolytic enzymes in the contaminated intestine and kidney.

Thermally-induced gels were made from white croaker (Pennahia argentata) meat in the presence of its organ extracts by pre-heating at 40 and 65°C for 20 min and subsequent heating at 85°C for 20 min. The breaking strength of the gels decreased with increasing concentrations of the intestinal extracts accompanying decomposition of myosin heavy chains. However, no significant changes in the gel strength occurred when the kidney extract was added.

The pepsin digestibility of thermal gel products made from white croaker (Pennahia argentata) muscle in associating with myosin polymerization levels.

Thermal gels were made from white croaker (Pennahia argentata) surimi at various polymerization levels of myosin heavy chains induced by suwari treatment at 38 °C for various time periods and subsequently heated at 85 °C for 20 min. Myosin heavy chain polymerization levels were also achieved in the presence of microbial transglutaminase (MTG) added at various concentrations in the surimi. The breaking strength and breaking strain rate were markedly increased during suwari treatment up to 60 min in accordance with the increased levels of myosin heavy chain polymerization.

Effects of point mutations on the structural stability of tuna myoglobins.

Structural stabilities of myoglobin (Mb) from several tuna fish species significantly differ from each other, although the amino acid sequence identities are very high (>95%), suggesting that limited number of substitutions greatly affect the stability of Mb. To address this hypothesis, attempts were made to elaborate recombinant tuna Mbs with point mutations on the different residues among fish Mbs. The expression plasmid constructs were based on bigeye tuna Mb cDNA sequence, and the recombinant proteins were expressed as GST-fusion proteins in Escherichia coli.

Cryptides: functional cryptic peptides hidden in protein structures.

Peptidergic hormones, neurotransmitters, and neuromodulators are extracellular signaling molecules that play central roles in physiological signal transmissions between various cells, tissues, and organs. These factors are primarily translated as inactive precursor proteins according to the genetic information. These precursor proteins are then cleaved by various proteases including signal peptidases and processing enzymes to produce matured bioactive factors.

Effect of amino acid replacements on the structural stability of fish myoglobin.

Structural stabilities of myoglobin (Mb) from several fish (scombridae) species differ significantly, although their amino acid sequence identity is very high (>95%), suggesting that only a few substitutions greatly affect the stability of Mb. Accordingly, recombinant Mbs with point mutation(s) derived from bigeye tuna Mb cDNA were expressed as GST-fusion proteins in the soluble fractions of Escherichia coli. After removal of the GST segment, the stability of five mutants, namely, P13A, I21M, V57I, A62G, and I21M/V57I, together with the wild type (WT) were investigated, taking temperature dependency of alpha-helical content and denaturant concentration dependency of Soret band absorbance as parameters.

Structural stabilities of recombinant scombridae fish myoglobins.

An expression system of recombinant myoglobins (Mb) of 3 scombridae fish species was constructed. The stability of these Mbs was compared with native Mbs purified from slow skeletal muscle. The addition of hemin during the cultivation of an Escherichia coli strain harboring a pGEX-2T expression vector was found to be necessary to prevent recombinant Mb from degrading and to attain its proper folding.

Characterization of bullet tuna myoglobin with reference to the thermostability-structure relationship.

Myoglobin (Mb) was isolated from bullet tuna (Auxis rochei) skeletal muscle and characterized from the viewpoint of the thermostability-structure relationship. Differential scanning calorimetry (DSC) measurement showed that the thermostability of bullet tuna Mb was the lowest among all the scombridae fish Mbs so far examined. The highest value (72.