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J Biol Chem, Vol. 274, Issue 1, 117-122, January 1, 1999
Conformational Change of the Catalytic Subunit of
Glucose-6-phosphatase in Rat Liver during the Fetal-to-Neonatal
Transition
Ferenc
Puskás §,
Paola
Marcolongo ,
Sharlene L.
Watkins ,
József
Mandl§,
Bernard B.
Allan¶,
Pamela
Houston¶,
Ann
Burchell¶,
Angelo
Benedetti , and
Gábor
Bánhegyi
From the Istituto di Patologia Generale,
Università di Siena, 53100 Siena, Italy, the
§ Department of Medical Chemistry, Semmelweis University of
Medicine, 1444 Budapest, Hungary, and the ¶ Department of
Obstetrics and Gynaecology, Ninewells Hospital and Medical School,
Dundee DD1 9SY, United Kingdom
The glucose-6-phosphatase system was investigated
in fetal rat liver microsomal vesicles. Several observations indicate
that the orientation of the catalytic subunit is different in the fetal liver in comparison with the adult form: (i) the phosphohydrolase activity was not latent using glucose-6-phosphate as substrate, and in
the case of other phosphoesters it was less latent; (ii) the
intravesicular accumulation of glucose upon glucose-6-phosphate hydrolysis was lower; (iii) the size of the intravesicular
glucose-6-phosphate pool was independent of the glucose-6-phosphatase
activities; (iv) antibody against the loop containing the proposed
catalytic site of the enzyme inhibited the phosphohydrolase activity in fetal but not in adult rat liver microsomes. Glucose-6-phosphate, phosphate, and glucose uptake could be detected by both light scattering and/or rapid filtration method in fetal liver microsomes; however, the intravesicular glucose-6-phosphate and glucose accessible spaces were proportionally smaller than in adult rat liver microsomes. These data demonstrate that the components of the glucose-6-phosphatase system are already present, although to a lower extent, in fetal liver,
but they are functionally uncoupled by the extravesicular orientation
of the catalytic subunit.
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.

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Copyright © 1999 by the American Society for Biochemistry and Molecular Biology.
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