Physiological relevance of the changing subunit composition and regulatory properties of the 6-phosphofructo-1-kinase isozyme pools during heart and muscle development |
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Authors: | George A Dunaway Thomas P Kasten |
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Institution: | (1) Department of Pharmacology, Southern Illinois University School of Medicine, P.O. Box 19230, 62794-9230 Springfield, Illinois, USA |
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Abstract: | During postnatal development, the subunit compositions of the 6-phosphofructo-l-kinase isozyme pools of heart and skeletal muscle are known to change. The isozyme pools from fetal muscle were composed of the L-type (60%), and M-type (36%) and C-type (4%) subunits and the isozymes from fetal and early neonatal heart contain nearly equal amounts of all three subunits. During postnatal development of both tissues, the proportion of the M-type subunit increases until it is the only type present in adult muscle and the major subunit in adult heart (7507o). The isozyme pool from fetal muscle exhibit a decreased affinity for fructose-6-P and a greater susceptibility to ATP inhibition compared to the M-rich isozymes which are subsequently present. The isozyme pools from fetal and early neonatal heart, if compared to the M-rich isozymes which are present later during heart development and to the fetal muscle isozymes, exhibited the least affinity for fructose-6-P and the greatest susceptibility to ATP inhibition. Comparison of the isozyme pools containing little or no C-type subunit with those from fetal and early neonatal heart clearly indicates that the presence of substantial levels of the C-type subunit imposed a decreased ability for fructose-2,6-P2 to both lower affinity for fructose-6-P and antagonize sensitivity to ATP inhibition. Although still not thoroughly appreciated, it appears that the changing nature of the isozyme pools in these tissues permits regulation of glucose metabolism in a manner which allows efficient utilization of nutritional opportunities and which adequately meets the energy requirements of each tissue at different stages of development.Abbreviations PFK
6-phosphofructo-l-kinase
- fructose-6-P
D-fructose-6-phosphate
- fr-t_ose-2,6-P2
D-fructose-2,6-bisphosphate |
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Keywords: | 6-phosphofructo-l-kinase development heart muscle metabolic regulation isozymes |
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