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J Biol Chem. 2003 Oct 24;278(43):41856-61. Epub 2003 Aug 11.

Brown adipose tissue Ca2+-ATPase: uncoupled ATP hydrolysis and thermogenic activity.

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Instituto de Ciências Biomédicas, Departamento de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, RJ 21941-590, Brazil.


In this report a sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) was identified in rats brown adipose tissue. Electrophoretic analysis of brown fat microssomal protein yields a 110-kDa 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 Ca2+ affinity and a much higher degree of ATPase/Ca2+ uncoupling. A SERCA enzyme is not found in white fat. Fatty acids promoted Ca2+ leakage from brown fat vesicles. The heat released during ATP hydrolysis was -24.7 kcal/mol when a Ca2+ gradient was formed across the vesicles membrane and -14.4 kcal/mol in the absence of a gradient. The data reported suggest that in addition to storing Ca2+ inside the endoplasmic reticulum, the Ca2+-ATPase may represent a source of heat production contributing to the thermogenic function of brown adipose tissue.

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