– UBASH3B contains a ubiquitin associated domain at the N-terminus, an SH3 domain, and a C-terminal domain with similarities to the catalytic motif of phosphoglycerate mutase. UBASH3B was found to inhibit endocytosis of epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor. UBASH3B interferes with CBL-mediated down-regulation and degradation of receptor-type tyrosine kinases. It promotes accumulation of activated target receptors, such as T-cell receptors and EGFR, on the cell surface. UBASH3B exhibits tyrosine phosphatase activity toward several substrates including EGFR, FAK, SYK, and ZAP7. Down-regulates proteins that are dually modified by both protein tyrosine phosphorylation and ubiquitination.