The function of Ensembl gene identifier ENSG00000012817 (KDM5D, lysine demethylase 5D) is as follows. Histone demethylase that specifically demethylates 'Lys-4' of histone H3, thereby playing a central role in histone code. Does not demethylate histone H3 'Lys-9', H3 'Lys-27', H3 'Lys-36', H3 'Lys-79' or H4 'Lys-20'. Demethylates trimethylated and dimethylated but not monomethylated H3 'Lys-4'. May play a role in spermatogenesis. Involved in transcriptional repression of diverse metastasis-associated genes; in this function seems to cooperate with ZMYND8. Suppresses prostate cancer cell invasion. Regulates androgen receptor (AR) transcriptional activity by demethylating H3K4me3 active transcription marks. {ECO:0000269|PubMed:17320160, ECO:0000269|PubMed:17320162, ECO:0000269|PubMed:17351630, ECO:0000269|PubMed:26747897, ECO:0000269|PubMed:27185910, ECO:0000269|PubMed:27427228, ECO:0000269|PubMed:27477906}.