IDENTIFICATION OF A 2ND HUMAN ACETYL-COA CARBOXYLASE GENE

Acetyl-CoA carboxylase (ACC), an important enzyme in fatty acid biosyn thesis and a regulator of fatty acid oxidation, is present in at least two isoenzymic forms in rat and human tissues. Previous work has esta blished the existence of a 265000 Da enzyme in both the rat and human (RACC265; HACC265) and a higher-molecular-mass species (275000-280000 Da) in the same species (RACC280; HACC275). An HACC265 gene has previo usly been localized to chromosome 17. In the present study, we report cloning of a partial-length human cDNA sequence which appears to corre spond to HACC275 and its rat homologue, RACC280, as judged by mRNA tis sue distribution and cell-specific regulation of mRNA/protein expressi on. The gene encoding this isoenzymic form of ACC has been localized t o the long arm of human chromosome 12. Thus, ACC is represented in a m ultigene family in both rodents and humans. The newly discovered human gene and its rat homologue appear to be under different regulatory co ntrol to the HACC265 gene, as judged by tissue-specific expression in vivo and by independent modulation in cultured cells in vitro.