Adenosine 3′,5′-cyclic phosphate, lipolysis and oxygen consumption in brown adipose tissue from newborn rabbits effect of cervical sympathectomy and of noradrenalin and theophylline in vitro, and the partial purification of an adenosine 3′,5′-cyclic phosphate-dependent protein kinase

A new procedure for the purification of phosphofructokinase using Blue Dextran-Sepharose is described. This allowed an approx. 1000-fold purification of phosphofructokinase from rat white and brown adipose tissue to be achieved in essentially a single step. The purified enzymes from both tissues were found to exhibit hyperbolic kinetics with fructose 6-phosphate, to be inhibited by ATP and citrate, and to be activated by 5′-AMP, phosphate and fructose 2,6-bisphosphate. The enzymes were phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase, and phosphorylation was found to be associated with increases in activity when the enzymes were assayed under appropriate sub-optimal conditions. In particular, the phosphorylated enzymes exhibited less inhibition by ATP and the white-adipose-tissue enzyme was more sensitive to activation by fructose 2,6-bisphosphate. It is suggested that an increase in the cytoplasmic concentration of cyclic AMP in tissues other than liver may result in an increase in glycolysis through the phosphorylation of phosphofructokinase by cyclic AMP-dependent protein kinase.

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EFFECT OF TEMPERATURE ON METABOLIC RATES OF LIVER AND BROWN FAT HOMOGENATES

Canadian Journal of Biochemistry ◽

10.1139/o67-207 ◽

1967 ◽

Vol 45 (11) ◽

pp. 1763-1771 ◽

Cited By ~ 9

Author(s):

Jane C. Roberts ◽

Robert E. Smith

Keyword(s):

Adipose Tissue ◽

Oxygen Consumption ◽

Brown Adipose Tissue ◽

Brown Fat ◽

Effect Of Temperature ◽

Metabolic Rates ◽

Brown Adipose ◽

Rate Of Oxygen Consumption ◽

Effects Of Temperature

The effects of temperature in vitro upon metabolic rates of homogenates of brown fat and liver from control and cold-acclimated rats have been examined over the range 10–37 °C. At all temperatures, brown adipose tissue exhibits a higher rate of oxygen consumption [Formula: see text] than does liver, α-ketoglutarate being used as substrate. At 10 °C, brown adipose tissue retains a larger percentage (36–38%) of its 37 °C metabolic rate than does liver (22–24%).Q10 values and energies of activation (Ea) have been determined and compared with other data reported for these tissues. At 20 °C, breaks appear in the Arrhenius plots for liver from both control and cold-acclimated rats and also for brown fat from control rats, but not for the brown fat from cold-acclimated rats. Thus brown adipose tissue from cold-acclimated rats retains relatively higher levels of respiration at temperatures below the 20 °C breaking point than does brown fat from control rats.In view of previously reported cold-induced increases in mass, vascularity, and [Formula: see text] of brown fat, this decreased temperature sensitivity in the cold-acclimated rats appears wholly consonant with the adaptive behavior of brown fat in its role as a thermogenic effector.

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