Protease responsible for KMT2A/MLL1 processing and activation (PubMed:14636557). It also activates KMT2D/MLL2 (By similarity). Through substrate activation, it controls the expression of HOXA genes, and the expression of key cell cycle regulators including CCNA1, CCNB1, CCNE1 and CDKN2A (By similarity) (PubMed:14636557). . This is the function of Ensembl gene identifier ENSG00000089123 (TASP1, taspase 1).