| Evidence for regulation of the tumor necrosis factor alpha convertase ( TACE ) by protein tyrosine phosphatase PTPH 1 . ^^^ Here we report that the protein tyrosine phosphatase PTPH 1 , which contains both a band 4 . 1 domain and a single PDZ domain , can interact with the cytoplasmic domain of TACE . ^^^ The interaction is mediated via binding of the PDZ domain of PTPH 1 to the COOH terminus of TACE . ^^^ In co expression experiments , significantly lower levels of TACE were observed in the presence of catalytically active forms of PTPH 1 compared with catalytically inactive forms of PTPH 1 . ^^^ Furthermore , phorbol ester stimulated shedding of the TACE substrate tumor necrosis factor alpha was decreased in cells expressing catalytically active PTPH 1 compared with inactive PTPH 1 . ^^^ |