Effect of Adenosine-Nucleotides and Their Derivatives on the Denaturation of Myofibrillar Proteins in vitro during Frozen Storage at −20°C

To investigate the effect of adenosine-nucleotides and their derivatives on the denaturation of myofibrillar proteins, 235 nmoles/mL adenosine-5′-diphosphate (ADP), adenosine-5′-monophosphate (AMP), inosine-5′-monophosphate (IMP), inosine (HxR), or hypoxantine (Hx), was added to 3 mg/mL actomyosin (AM) solution suspended in 0.10M KC1 solution and stored at ?20°C for 12 wk. The AM was extracted from milktish dorsal muscle. Protein denaturation was evaluated by measuring solubility, Ca-ATPase and Mg(EGTA)-ATPase activity of AM, by analyzing changes in electrophoretic profiles and transmission electron microscopy. Inosine and hypoxanthine accelerated protein denaturation compared to control samples. Infrared spectrum analyses indicated that negatively charged groups of these nucleotides interacted with amino or imino groups on AM after addition. ADP, AMP, and IMP had a protective effect on denaturation of AM during frozen storage at ?20°C.