Induction of Modori-Phenomenon (Thermal Gel Degradation) by A Latent Serine Proteinase

An attempt was made to substantiate a modori (thermal gel degradation) inducing effect of a latent serine proteinase. The proteinase was purified homogeneously from the sarcoplasmic fraction of threadfin bream muscle using a combination of DEAF-cellulose, Con A-Sepharose, ArgSepharose, Shim-pack HAC, and TSK-gel G3000SWXL column chromatographies. Its molecular weight was estimated as 77,000 by SDS-PAGE analysis and 70,000 by gel filtration using TSK-gel G3000SWXL. To examine the occurrence of modori-phenomenon, sols prepared from threadfin bream myofibrils lacking in modori-causing property were heated at 60•Ž in the absence or presence of the proteinase. Only in the presence of the proteinase, marked modori was observed by the puncture test and sensory tests for estimating the physical property of resulting gels, and breakdown of myosin heavy chain was also observed by SDS-PAGE analysis. This evidence clearly suggests that the proteinase is responsible for the modori-phenomenon occurring at 60•Ž.