Exploration of Myosin Heavy Chain Fragments within the Protein Network in Disintegrated Deep-Sea Bonefish <i>Pterothrissus gissu</i> Surimi Gel

A significant challenge in the surimi industry is the softening of surimi gel caused by proteolytic degradation of myosin heavy chain (MHC) during heating. Details of MHC fragmentation remain unclear despite being crucial to understanding the mechanism of surimi gel softening. This study employed in-gel digestion coupled with mass spectrometric analysis (GeLC–MS/MS) of the urea-soluble proteins from surimi gels from deep-sea bonefish Pterothrissus gissu to explore myosin heavy chain fragments within the protein network. More MHC fragments of ∼28, 48, 70, 150, and 190 kDa were found in softer P. gissu surimi gels. The results of the sequence mapping indicate that ∼150 and 190 kDa MHC fragments were generated by cleavage at the light meromyosin (LMM) region. The results of the present study, combined with our previous findings, suggest a differential distribution of MHC fragments in the disintegrated P. gissu surimi gel based on their size. Specifically, longer MHC fragments exist in the protein network, while shorter fragments (∼28, 48, and 70 kDa) and peptides derived from the LMM region are partially soluble in water.