CHARACTERIZATION OF ENZYMES OF VALINE CATABOLISM

Project: Research project

Description

The overall objective is to clarify the pathway of Beta-
hydroxyisobutyrate catabolism and provide insight into the
regulation of metabolism of this compound. The working
hypothesis is that beta-hydroxyisobutyrate is made from valine in
peripheral tissues and used by the liver for gluconeogenesis. It is
proposd that 3-hydroxyisobutyrate dehydrogenase (E.C. 1.1.1.31)
is important in controlling interorgan catabolism of beta-hy-
droxyisobutyrate. It is further proposed that an enzyme
catalyzing the same reaction as methylmalonate semialdehyde
dehydrogenase (E.C. 1.2.1.27) of pseudomonads is present in
mammalian tissues. Studies will be conductied with purified
enzymes, isolated hepatocytes, and intact animals in different
nutritional, hormonal, and developmental states. The detailed
specific aims are: (a) to clone and sequence cDNA for 3-hy-
droxyisobutyrate dehydrogenase; (b) to determine the effects of
nutritional, hormonal, and developmental states on tissue amounts
of 3-hydroxyisobutyrate dehydrogenase and its mRNA; (c) to
develop an enzymatic assay for beta-hydroxyisobutyrate based on
the reaction catalyzed by 3-hydroxyisobutyrate dehydrogenase; (d)
to determine effects of nutritional and hormonal states on blood
levels of beta-hydroxyisobutyrate; (e) to determine effects of
other substrates (ethanol, oleate, beta-hydroxybutyrate) and
hormones on the metabolism of beta-hydroxyisobutyrate by
isolated hepatocytes; (f) to determine whether tissue specific
isozymes of 3-hydroxyisobutyrate dehydrogenase exist; (g) to
determine whether some enzyme other than 3-hydroxyisobutyrate
dehydrogenase is responsible for the oxidation of R-3-
hydroxyisobutyrate (intermediate in thymine catabolism); (h) to
identify cysteine residue(s) involved in substrate binding by 3-
hydroxyisobutyrate dehydrogenase; (i) to isolate and characterize
rat liver methylmalonate semialdehyde dehydrogenase; (j) to clone
and sequence cDNA for methylmalonate semialdehyde
dehydrogenase; and (k) to determine the effects of nutritional,
hormonal, and developmental states on tissue amounts of
methylmalonate semialdehyde dehydrogenase and its mRNA. These studies should further our understanding of the possible role
of beta-hydroxyisobutyrate as a source of carbon for hepatic
gluconeogenesis, establish whether methylmalonate semialdehyde
dehydrogenase is present in tissues of higher organisms, and
explain the accumulation of beta-hydroxyisobutyrate and related
compounds under conditions of ketoacidosis and in various
inherited organic acidemias.
StatusFinished
Effective start/end date9/1/886/30/99

Funding

  • National Institutes of Health: $154,160.00
  • National Institutes of Health
  • National Institutes of Health: $128,234.00
  • National Institutes of Health: $135,663.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health

Fingerprint

valine
3-hydroxyisobutyryl-CoA hydrolase
metabolism
Valine
Coenzyme A
enzymes
Palmitoyl-CoA Hydrolase
hepatocytes
Oxidoreductases
Enzymes
3-hydroxybutyric acid
Isobutyrates
thymine
liver
3-hydroxyisobutyrate dehydrogenase
ketosis
gluconeogenesis
Metabolic Networks and Pathways
Inborn Genetic Diseases
oleic acid

ASJC

  • Medicine(all)