Copper amine oxidases (CAOs) are found in almost every living kingdom. AlthoughSaccharomyces cerevisiaeis one of the few yeast species that lacks an endogenous CAO, heterologous gene expression of CAOs from other organisms produces a functional enzyme. To begin to characterize their function and mechanisms of copper acquisition, two putativecao⁺genes fromSchizosaccharomyces pombewere expressed inS. cerevisiae. Expression ofspao1⁺resulted in the production of an active enzyme capable of catalysing the oxidative deamination of primary amines. On the other hand, expression ofspao2⁺failed to produce an active CAO. Using a functionalspao1⁺–GFPfusion allele, the SPAO1 protein was localized in the cytosol. Under copper-limiting conditions, yeast cells harbouring deletions of theMAC1,CTR1andCTR3genes were defective in amine oxidase activity. Likewise,atx1Δ null cells exhibited no CAO activity, whileccc2Δ mutant cells exhibited decreased levels of amine oxidase activity, and mutations incox17Δ andccs1Δ did not cause any defects in this activity. Copper-deprivedS. cerevisiaecells expressingspao1⁺required a functionalatx1⁺gene for growth on minimal medium containing ethylamine as the sole nitrogen source. Under these conditions, the inability of theatx1Δ cells to utilize ethylamine correlated with the lack of SPAO1 activity, in spite of the efficient expression of the protein. Cells carrying a disruptedccc2Δ allele exhibited only weak growth on ethylamine medium containing a copper chelator. The results of these studies reveal that expression of the heterologousspao1⁺gene inS. cerevisiaeis required for its growth in medium containing ethylamine as the sole nitrogen source, and that expression of an activeSchiz. pombeSPAO1 protein inS. cerevisiaedepends on the acquisition of copper through the high-affinity copper transporters Ctr1 and Ctr3, and the copper chaperone Atx1.