Project: Research project

Project Details


Methyl conjugation is an important pathway in the metabolism of drugs,
xenobiotics, endogenous compounds and neurotransmitters. The experiments
proposed are designed to enhance our understanding of the biological basis
for individual variations in methyl conjugation. Our laboratory has
already discovered genetic polymorphisms that regulate activities of the
O-methylating enzyme, catechol-O-methyltransferase (COMT) and the
S-methylating enzyme, thiopurine methyltransferase (TPMT) in man. We
propose to expand our studies of TPMT to include experiments with inbred
strains of mice with very different TPMT activities and experiments with
cultured human lymphocytes from subjects with different TPMT genotypes. In
addition, our studies of methyl conjugation will be extended to include the
enzyme histamine N-methyltransferase (HNMT). We have recently confurmed
that HNMT activity is present in an easily accessible human tissue, the
erythrocyte (RBC). We have developed a sensitive assay for the measurement
of RBC HNMT activity. One goal of this proposal is to determine whether
variations in the biochemical properties and regulation of HNMT in the
human RBC are influenced by inheritance. It will then be determined
whether the biochemical properties and regulation of HNMT in an easily
accessible tissue, the RBC, are similar to and are correlated with those of
HNMT in the kidney and liver, two less accessible human tissues. To
accomplish these goals, HNMT activity will be measured in RBCs of
first-degree ralatives, and the role of inheritance in regulating
variations in the level of activity will be determined. HNMT will be
purified from the human RBC, human kidney and human liver, and the
biochemical properties of the enzyme in those tissues will be compared.
Individual variation in RBC HNMT activities will be correlated with
variations in HNMT activities in samples of human kidney and liver obtained
during clinically-indicated nephrectomies and partial hepatectomies.
Monoclonal and polyclonal antibodies to human HNMT will be developed to
study the cellular localization of the enzyme in human organs and to study
mechanisms responsible for individual variations in the level of activity
of the enzyme. The results of these experiments will enhance our
understanding of the biological basis for individual variations in the
activities of enzymes that catalyze the S-and N-methylation of drugs,
xenobiotics, and endogenous compounds.
Effective start/end date7/1/803/31/20


  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)