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  • 1
    Electronic Resource
    Electronic Resource
    The subunit proportions and kinetic properties of 6-phosphofructo-1-kinase isozymes from rat heart atria and ventricle progressively change during aging (1991)
    Springer
    Molecular and cellular biochemistry 107 (1991), S. 39-45 
    Details
    ISSN: 1573-4919
    Keywords: 6-phosphofructo-1-kinase ; aging ; heart ; energy metabolism ; metabolic regulation ; isozymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Relative to 2–3 month rats, total 6-phosphofructo-1-kinase (PFK) activity in heart atria from 12 month rats declined 31%; but, by 24 months it was decreased by only 13%. PFK activities from 12 and 24 month ventricles relative to the 2–3 month rat were decreased by 40% and 30%, respectively. This change in PFK activity in each heart region was associated with alterations of subunit composition. In heart atria from 12 and 24 month rats when compared to 3 month rats, the levels of L-type subunit were not significantly different; but the levels of the M-type subunit were decreased by 43% and 38%, respectively. With respect to levels in 2–3 month atria, the C-type subunit in 12 month atria decreased by 27%; and at 24 months it increased by 31%. Making the same comparison for the heart ventricle at 12 and 24 months, L-type subunit decreased by 30% and 24% respectively; M-type subunit decreased by approximately 47%; and the C-type subunit increased 1.9 and 4.7 fold, respectively. These age-related changes of subunit composition in atrial and ventricular PFK isozyme pools led to changes in their kinetic and regulatory properties suggesting that the aged rat could exhibit a diminished capacity to produce ATP from glucose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02424574
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  • 2
    Electronic Resource
    Electronic Resource
    Physiological relevance of the changing subunit composition and regulatory properties of the 6-phosphofructo-1-kinase isozyme pools during heart and muscle development (1989)
    Springer
    Molecular and cellular biochemistry 87 (1989), S. 71-77 
    Details
    ISSN: 1573-4919
    Keywords: 6-phosphofructo-l-kinase ; development ; heart ; muscle ; metabolic regulation ; isozymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00421084
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