Identification of the alpha-aminoadipic semialdehyde dehydrogenase-phosphopantetheinyl transferase gene, the human ortholog of the yeast LYSS gene

In mammals, L-lysine is first catabolized to alpha -aminoadipate semialdehy de by the bifunctional enzyme alpha -aminoadipate semialdehyde synthase (AA SS), followed by a conversion to alpha -aminoadipate by alpha -aminoadipate semialdehyde dehydrogenase. In Saccharomyces cerevisiae, which synthesize rather than degrade lysine, the latter activity requires two distinct genes . LYS2 encodes the alpha -aminoadipate reductase activity, while LYS5 encod es a phosphopantetheinyl transferase activity that is required to activate Lys2p, We have identified a full-length human cDNA homologous to the yeast LYS5 gene. The cDNA contains an open-reading frame of 930 bp predicted to e ncode 309 amino acids, and the human protein is 26% identical and 44% simil ar to its yeast counterpart. In Northern blot analysis the cDNA hybridizes to a single transcript of approximately 3 kb in all tissues except testis, where there is an additional transcript of 1.5 kb. Expression is highest in brain followed by heart and skeletal muscle, and to a lesser extent in liv er. We further identified three human genomic BAC clones containing the hum an gene. Fluorescence in situ hybridization (FISH) analysis using the BAC c lones mapped the gene to chromosome 11q22 while alignment of the cDNA and g enomic sequences allowed partial identification of the intron-exon boundari es. Finally, using one-step homologous recombination in S. cerevisiae we ge nerated a lys5 knockout strain. Complementation studies in the yeast knocko ut demonstrate that the human homolog encodes alpha -aminoadipate dehydroge nase phosphopantetheinyl transferase activity. We hypothesize that defects in this gene may result in pipecolic acidemia. (C) 2001 Academic Press.