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protein tyrosine phosphatase-like pseudophosphatase domain of myotubularin related phosphoinositide phosphatase 9 Myotubularin related phosphoinositide phosphatase 9 (MTMR9) is enzymatically inactive and contains a C-terminal coiled-coil domain and an N-terminal PH-GRAM domain. Mutations have been associated with obesity and metabolic syndrome. In general, myotubularins are a unique subgroup of protein tyrosine phosphatases that use inositol phospholipids, rather than phosphoproteins, as substrates. MTMR9 is a pseudophosphatase that lacks the catalytic cysteine in its catalytic pocket. It forms complexes with catalytically active MTMR6, MTMR7 and MTMR8, and regulates their activities; the complexes display differential substrate preferences. The MTMR6/R9 complex serves to inhibit stress-induced apoptosis while the MTMR8/R9 complex inhibits autophagy.
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