Brown adipose tissue Ca 2 + - ATPase : Uncoupled ATP hydrolysis and thermogenic activity

In this report a sarco/endoplasmic reticulum Ca-ATPase (SERCA) was identified in rats brown adipose tissue. Electrophoretic analysis of brown fat microssomal protein yields a 110 kD band that is reactive to SERCA 1 antibody, but is not reactive to SERCA 2 antibodies. Nevertheless, the kinetics properties of the brown fat SERCA differ from the skeletal muscle SERCA 1 inasmuch they manifest a different Ca affinity and a much higher degree of ATPase/Ca uncoupling. A SERCA enzyme is not found in white fat. Fatty acids promoted Ca leakage from brown fat vesicles. The heat released during ATP hydrolysis was –24.7 Kcal/mol when a Ca gradient was formed across the vesicles membrane and -14.4 Kcal/mol in the absence of a gradient . The data reported suggest that the in addition to store Ca inside the endoplasmic reticulum, the Ca-ATPase may represent a source of heat production contributing to the thermogenic function of brown adipose tissue. by gest on N ovem er 9, 2017 hp://w w w .jb.org/ D ow nladed from