Fructose-1,6-diphosphatase activity in brown adipose tissue of the developing rat

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Abstract
An enzyme activity capable of converting fructose-1,6-diphosphate to fructose-6-phosphate was present in crude tissue extracts from rat brown adipose tissue. Mg2+ was essential for the expression of activity. EDTA (0.5 mM) increased the activity by 30%. Fructose-1,6-diphosphate in concentrations of 1 and 10 mM inhibited activity by 30 and 60%, respectively. A 65% inhibition was observed in the presence of 0.2 .mu.M 5'' AMP. The activity of the enzyme was measured in rat brown adipose tissue at different stages of development. It rose sharply between day 2 and day 6 and continued to increase reaching a maximum between 6 and 11 days. Thereafter the activity gradually declined to values observed prenatally. The normal development rise in activity could be prevented by chemical sympathectomy on day 2. This procedure had no effect when carried out on day 9. There was a significant increase in enzyme activity after cold adaptation. The possible physiological significance of this enzyme in brown adipose tissue was discussed.