Thermal regulation of gluconeogenesis in the giant scallop, Placopecten magellanicus (Gmelin)
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Comp. Biochem. PhysioL, 1971, Vol. 39B, pp. 163 to 165. Pergamon Press. Printed in Great Britain SHORT COMMUNICATION THERMAL REGULATION OF GLUCONEOGENESIS IN THE GIANT SCALLOP, PLACOPECTEN MAGELLANICUS (GMELIN) P. J. A. O'DOHERTY* and L. A. W. FELTHAM Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, Canada (Received 30 October 1970) Abstract--1. The inhibition of fructose diphosphatase by AMP and the activation of phosphoenolpyruvate carboxykinaseby cyclicAMP in the adductor muscle were found to be temperature-dependent. 2. The significance of these findings is discussed. INTRODUCTION IT HAS been shown by Behrisch & Hochachka (1969) that, in a vertebrate poikilo- therm, AMP inhibition of fructose diphosphatase was temperature-dependent. This present communication examines the effect of temperature on the gluconeogenic enzymes of the adductor muscle of the giant scallop. MATERIALS AND METHODS Particulate-free supematant of the adductor muscle was prepared, and the enzymes fructose diphosphatase and phosphoenolpyruvate carboxykinase (PEP carboxykinase) assayed, as previously described (O'Doherty & Feltham, 1971). RESULTS The effect of temperature on the inhibition of fructose diphosphatase by AMP is shown in Fig. 1. At 3°C, which is taken as the lower environmental temperature, the inhibition at 0.5/~m is 20 per cent of what it is at 10°C. The AMP did not affect the thermal stability of the enzyme. In the case of PEP carboxykinase the activation at a cyclic AMP concentration of 0.3/zm was six times as much at 3°C as at 10°C (Fig. 2). DISCUSSION This is the first report of thermal studies on the enzymes of scallops. The temperature-dependence of the cyclic AMP activation of PEP carboxykinase and the AMP inhibition of FDPase could be an interesting mechanism of metabolic * Present address : Charles H. Best Institute, University of Toronto, Toronto 5, Canada. 163
Transcript of Thermal regulation of gluconeogenesis in the giant scallop, Placopecten magellanicus (Gmelin)
Comp. Biochem. PhysioL, 1971, Vol. 39B, pp. 163 to 165. Pergamon Press. Printed in Great Britain
SHORT COMMUNICATION
THERMAL REGULATION OF GLUCONEOGENESIS IN THE GIANT SCALLOP, PLACOPECTEN MAGELLANICUS
(GMELIN)
P. J. A. O'DOHERTY* and L. A. W. FELTHAM
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Newfoundland, Canada
(Received 30 October 1970)
Abstract- -1 . The inhibition of fructose diphosphatase by AMP and the activation of phosphoenolpyruvate carboxykinase by cyclic AMP in the adductor muscle were found to be temperature-dependent.
2. The significance of these findings is discussed.
INTRODUCTION IT HAS been shown by Behrisch & Hochachka (1969) that, in a vertebrate poikilo- therm, AMP inhibition of fructose diphosphatase was temperature-dependent.
This present communication examines the effect of temperature on the gluconeogenic enzymes of the adductor muscle of the giant scallop.
MATERIALS AND METHODS
Particulate-free supematant of the adductor muscle was prepared, and the enzymes fructose diphosphatase and phosphoenolpyruvate carboxykinase (PEP carboxykinase) assayed, as previously described (O'Doherty & Feltham, 1971).
RESULTS The effect of temperature on the inhibition of fructose diphosphatase by AMP
is shown in Fig. 1. At 3°C, which is taken as the lower environmental temperature, the inhibition at 0.5/~m is 20 per cent of what it is at 10°C. The AMP did not affect the thermal stability of the enzyme.
In the case of PEP carboxykinase the activation at a cyclic AMP concentration of 0.3/zm was six times as much at 3°C as at 10°C (Fig. 2).
DISCUSSION This is the first report of thermal studies on the enzymes of scallops. The
temperature-dependence of the cyclic AMP activation of PEP carboxykinase and the AMP inhibition of FDPase could be an interesting mechanism of metabolic
* Present address : Charles H. Best Institute, University of Toronto, Toronto 5, Canada.
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164 P .J .A . O'DOHERTY AND L. A. W. FELTHAM
>
I 0 0
50
~3 o
10 °
] E I I J o o.t o.a 03 04 0.5 [AMP] M x 106.
F l a . 1. I n h i b i t i o n o f F D P a s e b y A M P . T h e e n z y m e was assayed in particulate- free supernatant containing 0"2 m g protein/ml.
I00
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3 °
2 5
1 0 o
o o.I o.a 0.3 0.4 o.s [Cyclic AMP] M x 10 -3
F I c . 2. A c t i v a t i o n o f PEP carboxykinase by cyclic A M P . T h e enzyme was assayed in particulate-free supernatant containing 0"2 mg protein/ml.
control in the adductor muscle. It has been established that in molluscs, gluco- neogenesis is favoured during low-temperature acclimatization. This could explain why at 3°C the inhibition of fructose diphosphatase by A M P is slight and why cyclic A M P can activate PEP carboxykinase. These two enzymes are important in gluconeogenesis in the scallop (O'Doherty & Feltham, 1971). Behrisch &
GLUCONEOGENESIS I N THE GIANT SCALLOP 165
Hochachka (1969) have shown that the AMP inhibition of fructose diphosphatase is also temperature-dependent in a vertebrate poikilotherm. Thus it appears temperature may be an important parameter of metabolic regulation in the scallop.
Acknowledgements.--We wish to thank Dr. F. A. Aldrich of the University's Marine Sciences Research Laboratory for all the facilities granted and the Fisheries Research Board of Canada for financial support.
REFERENCES
BEHRISCH H. W. & HOCI-IACHKA P. W. (1969) Temperature and the regulation of enzyme activity in poikilotherrns. Biochem. aY. 111, 287-295.
O'DOHERTY P. J. A. & FELTHaM L. A. W. (1971) Glycolysis and gluconeogenesis in the giant scallop, Placopecten magellanicus (Gmelin). Comp. Biochem. Physiol. 311, 543-551.
Key Word Index--Gluconeogenic enzymes; temperature regulation; giant scallop; Placopacten mageUanicus.
