Species-specific thermal denaturation pattern of fish myosin when heated as myofibrils as studied by myosin subfragment-1 and rod denaturation rates

Abstract

Thermal denaturation of myofibrils from various species of fish was investigated by measuring ATPase inactivation, myosin aggregation, myosin subfragment-1 (S-1) and rod denaturation rates as studied by chymotryptic digestion. Decrease in monomeric myosin (myosin aggregation) was always faster than the ATPase inactivation for all myofibrils tested. The relative denaturation rate of rod to that of S-1 differed from species to species. Preceded denaturation of rod was observed with some species, and the opposite was true with other species. The denaturation pattern was explained by the different magnitude of S-1 stabilization by F-actin in myofibrils at low salt medium. Myofibrils which receive a great stabilization by F-actin as studied by ATPase inactivation showed the preceded rod denaturation pattern, and vice versa. S-1 portion, not F-actin, determined the different stabilization of S-1 by F-actin in myofibrils.

Thermal denaturation profiles of catfish and tilapia myofibrils as affected by pH for heating

“…Moreover, slow decrease of rod production found with tilapia myofibrils was accompanied by the generation of aggregates. It is reported that S-1 and rod denaturation profile was fish-species specific [4]. The above conclusion including ours was led based on the heating experiments in 0.1 M NaCl, pH 7.5.…”

“…S-1 and rod denaturation pattern was dependent on the pH for heating. It has been proposed 15 that S-1 and rod denaturation pattern is fish species-specific [4], which was concluded from the experimental results conducted at pH 7.5. We added a modified proposal that S-1 and rod denaturation pattern is also affected by the factors that affects myosin filament structure, pH in this paper.…”

“…Chymotryptic digestion is a very useful technique to study myosin denaturation occurring on subfragment-1 (S-1) and rod portion of myosin. It has also been reported that S-1 and rod denaturation proceed differently and the pattern is fish species-specific [4]. The rod denaturation studied by chymotryptic digestion is based on the fact that native myosin in filamentous form in myofibrils is cleaved selectively only at S-1/rod junction.…”

“…It is reported that the stabilization extent by F-actin binding is fish species-dependent [4]. To understand the stability in meat, thermal stability of myosin 4 in myofibrils as well as in isolated form should be studied by measuring thermal inactivation of Ca 2+ -ATPase.…”

“…The rates at 0.1 M and at 2 M NaCl were measured to access the rates with and without protection by F-actin, respectively ( To investigate rod denaturation as well as S-1 when heated as myofibrils, change in the chymotryptic digestion pattern upon their heating was studied. We also studied whether the fragments produced from the heated myofibrils are all monomer because rod found in the digest sometimes contains aggregated one [4]. Aggregates are well removed from the digest by applying ammonium sulfate fractionation at 40 % saturation, in which monomeric rod was recovered in the supernatant.…”