| Autor: |
Tran, Cam T.L., Fox, Margaret F., Vallance, Patrick, Leiper, James M. |
| Zdroj: |
Genomics; August 2000, Vol. 68 Issue: 1 p101-105, 5p |
| Abstrakt: |
Endogenously produced asymmetrically methylated arginine residues are competitive inhibitors of all three isoforms of nitric oxide synthase (NOS). The enzyme dimethylarginine dimethylaminohydrolase (DDAH) specifically hydrolyzes these asymmetrically methylated arginine residues to citrulline and methylamines. Previously we have proposed that regulation of asymmetric methylarginine concentration by DDAH may provide a novel mechanism for the regulation of NOS activity in vivo.Recently we reported the cloning of human DDAH and identified a novel human DDAH isoform (DDAH I and DDAH II, respectively). Here we report that the DDAH1gene maps to chromosome 1p22 and confirm that DDAH2maps to the MHC III region of chromosome 6p21.3. Extensive analysis of the distribution of DDAH1and DDAH2mRNA in 50 human tissues indicates differential expression of DDAH isoforms in brain regions, in immune cells, and during development. DDAH2expression predominates in highly vascularized tissues that express the endothelial NOS isoform and in immune tissues that can express iNOS. Whereas DDAH2is expressed at relatively high levels in all fetal tissues examined, DDAH1expression varies little between fetal and adult tissues. The chromosomal localization of the DDAHs is consistent with gene duplication, and consistent with this, comparison of the gene structures indicates that the intron/exon organization is highly conserved. Phylogenetic analysis of DDAH sequences from diverse species suggests that DDAH gene duplication occurred prior to the emergence of bony fish some 400 million years ago. Overall the data suggest that DDAH2may be the more ancient of the two genes. |
| Databáze: |
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