The long term objective is to understand the role of 5- aminolevulinate synthase (ALAS), both at the enzyme and gene levels, in the regulation of heme biosynthesis in differentiating erythrocytes. ALAS catalyzes the first and rate limiting step in heme biosynthesis, the PLP-dependent reaction of glycine and succinyl-CoA to yield aminolevulinic acid, CoA and CO2. ALAS synthesis, although ubiquitous, occurs predominately in erythrocytes and hepatocytes, where demands are greater because of the synthesis of hemoglobin and cytochrome P-450, respectively. The erythroid-specific isoform of ALAS (ALAS-E) is expressed concomitantly with the differentiation and maturation of the erythroid cells. Recently a heterozygous group of point mutations in the catalytic domain of the ALAS-E enzyme has been found to cause the human genetic disorder X-linked sideroblastic anemia (XLSA). Characterization of the molecular mechanisms of the ALAS- catalyzed reaction and of the regulation of the expression of the ALAS-E gene are essential to design improved therapies for XLSA patients and/or for improved diagnosis for at-risk family members. Studies projected for the next four years will utilize chemical, biochemical, physical and molecular biological approaches to address three major specific aims: i) to define the role of K313 in the mammalian erythroid ALAS-catalyzed reaction; ii) to identify the functionally important residues of the glycine loop in the PLP cofactor binding site of ALAS; and iii) to evaluate transcriptional regulation of the mammalian erythroid ALAS (ALAS) gene. Results from these studies will provide the first characterization of the function and mechanism of ALAS at the molecular level and will elucidate the regulatory mechanism(s) of expression of the ALAS-E in differentiation erythrocytes. Significantly, they will provide the framework for the interpretation of the already identified ALAS-E genetic mutations associated with XLSA.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK052053-03
Application #
2856801
Study Section
Biochemistry Study Section (BIO)
Program Officer
Badman, David G
Project Start
1997-01-01
Project End
2000-12-31
Budget Start
1999-02-15
Budget End
1999-12-31
Support Year
3
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of South Florida
Department
Biochemistry
Type
Schools of Medicine
DUNS #
City
Tampa
State
FL
Country
United States
Zip Code
33612
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