IDENTIFICATION OF A PROTEIN-TYROSINE-PHOSPHATASE (SHP1) DIFFERENT FROM THAT ASSOCIATED WITH ACID-PHOSPHATASE IN RAT PROSTATE

Using [P-32]poly(Glu,Tyr) as substrate, we have identified, for the fi rst time, in the rat prostatic gland a protein-tyrosine phosphatase ac tivity different from that associated with prostatic acid phosphatase, Concanavalin A-Sepharose 4B was used to separate the two protein-tyro syl phosphatases activities, The activity retained by the lectin had c haracteristics of the prostatic acid phosphatase, It was sensitive to inhibition by PNPP and the optimum pH shifted towards physiological va lues when [P-32]poly(Glu,Tyr) was used as substrate, However, the majo r protein-tyrosine phosphatase activity was not retained by the lectin , and corresponded, at least in part, to SHP1 as probed by the presenc e of the protein, its mRNA and the loss of PTPase activity after immun odepletion of SHP1, This enzyme is localized within the epithelial cel ls, Thus, the coexistence of two protein-tyrosine phosphatase activiti es in rat prostate, one associated with the acid phosphatase and the o ther related to SHP1, makes it necessary to analyze the importance of both activities in vivo and their possible function regarding prostati c cell growth and its regulation. (C) 1997 Federation of European Bioc hemical Societies.