Project: Research project

Project Details


Acquired lactose intolerance is a common deficiency found in certain human
populations; it results from an absence of the disaccharide lactase in the
brush border of the small intestine. Congenital sucrase and lactase
deficiencies also exist but are more rare. The appearance of these
disaccharidases is well regulated both developmentally and during
maturation of intestinal cells. We propose to apply the techniques of
modern biochemical genetics to study the molecular basis for the regulation
during development and cell maturation as well as the inactivity in
disaccharide intolerance syndromes. The enzyme complexes lactase-phlorizin
hydrolase (L-P) and sucrase-isomaltase (S-I) will be isolated from rabbit
intestine and antibodies prepared against them. The mRNAs for these
polypeptides will be cloned as cDNA plasmids, using hybrid-selected in
vitro translation as a screening procedure. Libraries of rabbit and human
DNA will be screened by hybridization with the cDNA plasmids to isolate the
genes for S-I and L-P. We will determine whether or not the S-I and L-P
are synthesized as a large precursor containing both subunits, and what the
structure of the putative hybrid gene is. The nucleotide sequence of the
cDNA plasmids and portions of the genes will be determined. The regulated
steps in disaccharidase gene expression will be determined by using the
gene- and protein-specific probes to measure the concentrations of all
intermediates in expression in neonatal versus adult intestinal cells and
in crypt versus villus cells. These same probes will also be used to
identify which step is blocked in disaccharidase deficiency, i.e., gene
deletion, transcription, RNA processing and transport, translation or
posttranslational processing.
Effective start/end date1/1/8312/31/86


  • National Institutes of Health

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