The function of Ensembl gene identifier ENSG00000115107 (STEAP3, STEAP3 metalloreductase) is as follows. Integral membrane protein that functions as a NADPH-dependent ferric-chelate reductase, using NADPH from one side of the membrane to reduce a Fe(3+) chelate that is bound on the other side of the membrane (PubMed:26205815). Mediates sequential transmembrane electron transfer from NADPH to FAD and onto heme, and finally to the Fe(3+) chelate (By similarity). Can also reduce Cu(2+) to Cu(1+) (By similarity). Mediates efficient transferrin-dependent iron uptake in erythroid cells (By similarity). May play a role downstream of p53/TP53 to interface apoptosis and cell cycle progression (By similarity). Indirectly involved in exosome secretion by facilitating the secretion of proteins such as TCTP (PubMed:15319436, PubMed:16651434). {ECO:0000250|UniProtKB:Q5RKL5, ECO:0000250|UniProtKB:Q687X5, ECO:0000250|UniProtKB:Q8CI59, ECO:0000269|PubMed:15319436, ECO:0000269|PubMed:16651434, ECO:0000269|PubMed:26205815}.