The rapid post-mortem softening of abalone muscle is primarily attributed to collagen degradation mediated by matrix metalloproteinases (MMPs), although the synergistic mechanisms of different MMPs remain inadequately understood. In this study, we heterologously expressed MMP-3 and MMP-16 to investigate their combined effects on in vitro degradation of type I collagen and collagen fibers and then analyzed degradation products via mass spectrometry to elucidate the mechanism. Our findings showed that both enzymes degraded collagen individually, but their combined action accelerated collagen fiber degradation, causing more comprehensive breakdown. Mass spectrometry analysis revealed that MMP-3 initiated degradation by cleaving collagen telopeptides and disrupting the triple helix, facilitating MMP-16 infiltration into relaxed fibers to promote extensive proteolysis. This study elucidates a synergistic loosening-then-degradation mechanism of MMP-mediated collagen degradation, which underlies post-mortem muscle softening of abalone and thus provides a theoretical basis for seafood preservation strategies.
Zhang et al. (2026) studied this question.