TISSUE DISTRIBUTION OF ACETYL-COA CARBOXYLASE IN LEAVES OF LEEK (ALLIUM-PORRUM L.)

The distribution of acetyl-CoA carboxylase between the epidermal and m esophyll layers of leek leaves was determined. The specific activity o f acetyl-CoA carboxylase was approximately three-fold higher in extrac ts of the epidermis than in those from the mesophyll layer. Four promi nent biotinylated polypeptides of approximate molecular masses 240, 85 , 37, and 35 ku (kDa) were detected in leaf extracts. The biotin-conta ining subunit of the homomeric acetyl-CoA carboxylase, the 240-ku biot inylated polypeptide, accumulates exclusively in the epidermis of leek leaves. Three of the subunits of the heteromeric acetyl-CoA carboxyla se (the biotin carboxyl carrier, the biotin carboxylase, and beta-subu nit of the carboxyltransferase) were equally abundant in leek mesophyl l and epidermal tissues. These data indicate that leek leaves contain two structurally distinct isozymes of acetyl-CoA carboxylase, one of w hich, the homomeric form, is restricted to the epidermis.