AJP - Endocrinology and Metabolism, Vol 262, Issue 5 E608-E618, Copyright © 1992 by American Physiological Society
Pyruvate carboxylase in genetic obesity
C. J. Lynch, K. M. McCall, M. L. Billingsley, L. M. Bohlen, S. P. Hreniuk, L. F. Martin, L. A. Witters and S. J. Vannucci
Department of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, Hershey 17033.
Immunoblotting and protein microsequencing were used to identify several
adipocyte proteins expressed in an obesity-related fashion in the Zucker
rat. One of these was a 116-kDa particulate protein (p116). The p116 levels
in adipocytes from 5- to 7-wk-old obese Zucker rats were two- to fivefold
higher on a per milligram of protein basis than levels in lean animals and
decreased after the induction of streptozotocin-induced diabetes mellitus.
This suggests the change may be related to the actions of insulin. Hepatic
levels of p116 did not change. The p116 was purified to homogeneity from
obese Zucker rat adipocytes, and polyclonal antisera were prepared against
the purified protein in rabbits. Microanalysis of electroblotted p116
proteolytic fragments suggested that p116 was pyruvate carboxylase (PC).
Other evidence that p116 was PC included the following: 1) p116 contained
biotin, 2) p116 in particulate subcellular fractions was soluble after
freeze-lysis, 3) antibodies to p116 reacted with purified hepatic PC, 4)
p116 and purified hepatic PC had identical pI and relative molecular weight
values, and 5) similar changes were detected in adipocyte p116 and PC
enzyme activity during obesity and after the induction of
streptozotocin-induced diabetes mellitus. Increased adipose tissue PC
probably contributes to the increased lipogenic capacity of young obese
Zucker rat adipocytes.
