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Maximal Activities of Enzymes of Energy Metabolism in Cephalopod Systemic and Branchial Hearts
William R. Driedzic, Bruce D. Sidell, J. M. Stewart and Ian A. Johnston
Vol. 63, No. 3 (May - Jun., 1990), pp. 615-629
Published by: The University of Chicago Press. Sponsored by the Division of Comparative Physiology and Biochemistry, Society for Integrative and Comparative Biology
Stable URL: http://www.jstor.org/stable/30156232
Page Count: 15
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The maximal in vitro activities of enzymes of energy metabolism were assessed in systemic ventricle and the branchial hearts of the cephalopods Loligo forbesi, Sepia officinalis, Eledone cirrhosa, and Octopus vulgaris. Within each species, activity levels of enzymes of glycolysis (hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase, and octopine dehydrogenase), citrate synthase, cytochrome oxidase, and total ATPase were higher in the systemic ventricle than in branchial hearts. The greater metabolic potential is consistent with the higher levels of pressure development and subsequent energy demand in the ventricle than in branchial hearts. The systemic ventricle is nourished by oxygenated blood, whereas branchial hearts receive deoxygenated venous blood. Despite differences in oxygen delivery, there is no suggestion from the enzyme profile that anaerobic metabolism is enhanced in branchial hearts. Pairwise regressions were assessed for all marker enzymes from ventricles and branchial hearts of the four species. There are strong linear correlations between phosphofructokinase and citrate synthase activities, and between hexokinase and cytochrome oxidase activities. This suggests that, as interspecific demand for carbon to support the citric acid cycle is increased, there is a concomitant expansion of carbohydrate flux. Consideration of the ventricle alone reveals higher activity levels of phosphofructokinase, citrate synthase, and ATPase in decapods than in octopods. This is consistent with the greater sustainable swimming capability of the former group and may reflect maximum rates of cardiac energy metabolism.
Physiological Zoology © 1990 The University of Chicago Press