Thermal Denaturation of Tilapia Myosin and Its Subunits as Affected by Constantly Increasing Temperature

Abstract

Purified tilapia myosin was digested with α-chymotrypsin and purified to obtain heavy meromyosin (HMM) and light meromyosin (LMM). Biochemical properties of tilapia myosin, HMM, and LMM were characterized. Surface hydrophobicity (S(o) ) showed an increase for myosin and HMM between 30 and 40 °C and reached a plateau at 70 °C. LMM, in a small magnitude, also showed a continuous increase to 70 °C. Total sulfhydryl content (TSH) demonstrated that the SH residue content of HMM was nearly double that of LMM. Surface reactive sulfhydryl groups (SRSH) for myosin and HMM were relatively unchanged from 10 to 30 °C but increased from 30 to 50 °C. The exposure of buried hydrophobic and sulfhydryl groups of myosin and HMM increased as the myosin and HMM were constantly heated. However, the TSH and SRSH results indicated that the stability of LMM was likely due to its α-helix conformation. Reducing and nonreducing sodium dodecylsulfate-polyacryamide gel electrophoresis helped to understand the role of disulfide bonds in thermal aggregation of tilapia myosin, HMM, and LMM.