Study on collagenolytic mechanism of endogenous matrix metalloproteinase-2 in grass carp (Ctenopharyngodon idella)

Abstract

Texture is an important characteristic for fishery products, influencing quality classification and commercial value. Matrix metalloproteinases (MMPs) are deemed to participate in collagenolysis of postmortem fish flesh, whereas its mechanism is still unclear. This study revealed that a 66 kDa enzyme with gelatinolytic activity was separated from grass carp (Ctenopharyngodon idella) by ammonium sulfate precipitation technique and column chromatographic method, and identified as MMP-2 by liquid chromatography coupled with mass spectrometry analysis. In vitro experiments revealed that some collagen fibril bundles and individual fibrils were disintegrated from collagen fibers after digestion of MMP-2 for 48 h, along with a release of pyridinium cross-links (19.99 ± 1.02 %), hydroxyproline (15.04 ± 0.03 %) and glycosaminoglycan (11.21 ± 0.03 %). Meanwhile, MMP-2 treated samples mostly remained the triple-helical domain of collagen after treatment for 48 h, whereas their thermal stability was reduced. Furthermore, collagen fibers with high-level structures were more resistant to hydrolysis than collagen monomer and gelatin. All bands of gelatin and 90 % of collagen monomer were digested in 45 min and 4 h respectively. All these results suggested that MMP-2 might take part in the breakdown of collagen fibers by the destruction of cross-links, and the degradation of collagen molecules and proteoglycans in textural deterioration of refrigerated grass carp.