J. Biochem, 1988, Vol. 103, No. 2 309-312
© 1988 Japanese Biochemical Society
research-article |
Comparison of Sarcoplasmic Reticulum Ca2+-Adenosine Triphos-phatase from Vitamin E-Deficient Dystrophic Rabbit Skeletal Muscle with Iron-Ascorbate-Treated and Untreated Enzyme1
Department of Biochemistry,Mahidol University Rama 6 Road, Bangkok 10400, Thailand
2To whom correspondence should be addressed.
Sarcoplasmic reticulum Ca2+ATPase from rabbit skeletal muscle has an Arrhenius curve of enzyme activity with a discontinuity at about 20°C. Preparations treated with FeSO4 and ascorbic acid and from a vitamin E-deficient dystrophic rabbit have 22% of the normal activity and a linear Arrhenius curve (Promkhatkaew, D., Komaratat, P., & Wilairat, P. (1985) Biochem. Int. 10, 937–943). All three preparations were cross-linked to the same extent by dimethyl suberimidate and copper-phenanthroline reagent at temperatures above and below the temperature of the Arrhenius discontinuity. Both iron-ascorbate-treated Ca2+ -ATPase and that from a vitamin E-deficient animal had 50% of the normal sulfhydryl content, but the disulfide and free amino contents were unaltered. These observations suggest that loss of sulfhydryl groups through lipid peroxidation, both in vivo and in vitro, resulted in reduction of Ca2+ -ATPase activity and loss of the break in the Arrhenius plot. Changes in Ca2+ -ATPase polypeptide aggregational state could not account for the discontinuity in the Arrhenius curve as revealed by the similar extent of cross-linking of the three enzyme preparations at temperatures above and below the temperature of the Arrhenius discontinuity.
1This study was supported by a research grant from Mahidol University, Bangkok, Thailand.