IDENTIFICATION OF HUMAN ACETYL-COA CARBOXYLASE ISOZYMES IN TISSUE ANDIN BREAST-CANCER CELLS

1. In the rat, acetyl-CoA carboxylase (ACC), a rate-limiting enzyme in fatty acid metabolism, exists as at least two different isozymes (M(r ) 265,000 and 280,000) that display distinct tissue-specific distribut ion and regulation. 2. Based on the study of human tissue and human-de rived breast cancer cell lines by enzyme isolation and protein blottin g techniques, we have now identified two human isoforms of M(r) 265,00 0 (HACC 265) and 275,000 (HACC 275), each of which is homologous to on e of the rat isozymes. 3. Human breast carcinoma cell lines show varia ble expression of these two isoforms, mirrored in the estimation of AC C acetyl-CoA kinetics.