Properties of pyruvate dehydrogenase of rat mammary tissue and its changes during pregnancy, lactation and weaning

Author:

Coore Haldane G.1,Field Barbara1

Affiliation:

1. Department of Biochemistry, University of Birmingham, Birmingham B15 2TT, U.K.

Abstract

Pyruvate dehydrogenase of rat mammary tissue showed many of the regulatory properties of the analogous enzyme in other mammalian tissues. It was inactivated in the presence of low concentrations of ATP and this rate of inactivation was slowed if pyruvate or PP1 was also present. Reactivation by Mg2+ in the presence of low concentrations of Ca2+ occurred over a similar time-course. The Km value for Mg2+ in this process was about 2mm. The enzyme was assayed in extracts of freeze-clamped mammary glands removed from pregnant, lactating or recently weaned rats under halothane anaesthesia. Both the initial activity and the activity after full activation (‘total enzyme activity’) were determined. The former parameter, when expressed on a DNA basis, varied within a range of 40 times its lowest value. Maximum total enzyme activity was about 1 unit/g wet wt. The total enzyme activity and the fraction in the active form increased in step from pregnancy to mid-lactation, remained elevated until the end of lactation and then fell steeply within 3 days after weaning. The correlation of these two parameters of enzyme activity may indicate a common regulatory factor or else an interdependence arising from inherent properties of the multi-enzyme complex.

Publisher

Portland Press Ltd.

Subject

Cell Biology,Molecular Biology,Biochemistry

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1. Bioenergetic pathways in tumor mitochondria as targets for cancer therapy and the importance of the ROS-induced apoptotic trigger;Molecular Aspects of Medicine;2010-02

2. Lipid metabolism in the lactating mammary gland;Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism;1997-08

3. Long-term regulation and promoter analysis of mammalian pyruvate dehydrogenase complex;Alpha-Keto Acid Dehydrogenase Complexes;1996

4. Development and Molecular Biology of Mammalian Pyruvate Dehydrogenase Complex;Endocrine and Biochemical Development of the Fetus and Neonate;1990

5. Genetic Defects in Human Pyruvate Dehydrogenase;Annals of the New York Academy of Sciences;1989-12

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