Molecular Cloning of cDNAs Encoding Human Carnitine Acetyltransferase and Mapping of the Corresponding Gene to Chromosome 9q34.1

Using a combination of PCR screening of cDNA libraries and reverse transcription PCR, we have cloned three overlapping DNA fragments that encode human carnitine acetyltransferase (CAT), a key enzyme for metabolic pathways involved with the control of the acyl-CoA/CoA ratio in mitochondria, peroxisomes, and endoplasmic reticulum. The resulting cDNA (2436 bp) hybridizes to a mRNA species of ∼2.9 kb that is particularly abundant in skeletal muscle and encodes a 68-kDa protein containing a peroxisomal targeting signal. The sequence matches those of several tryptic peptides obtained from purified human liver CAT and shows striking similarities with other members of the carnitine/choline acetyltransferase family very distant throughout evolution. CAT cDNA has also been used for fluorescence in situ hybridization on metaphase spreads of human chromosomes, and the corresponding gene, CAT1 , has been mapped to chromosome 9q34.1.