Cell surface ferroxidase; part of the reductive iron assimilatory system (RIA), a siderophore-independent high affinity iron uptake mechanism (PubMed:15504822). Required to oxidize Fe(2+) and release it from the transporter (By similarity). Expression is up-regulated during iron starvation and is controlled by the GATA-type transcription factor sreA (PubMed:15504822, PubMed:18721228). Belongs to the multicopper oxidase family.