If more propanol is made, then it means less of the a-keto butyrate would be channelled into ethyl butanoate. Indeed, the results show that significantly less ethyl butanoate is formed when mitochondrial Cat2p is overexpressed. Com- pared with mitochondrial Cat2p, overexpression of cytosolic Cat2p resulted in minor decreases in the formation of some esters. The reason for this smaller contribution of cytosolic Cat2p to ester synthesis is unclear. We expected this cyto- solic isoform to have a greater effect than the mitochondrial isoform because Atf1p, responsible for the major part of volatile acetate ester production in yeast, is localized in lipid particles in the cytosol