TARTRATE-RESISTANT ACID-PHOSPHATASE FROM HUMAN OSTEOCLASTOMAS IS TRANSLATED AS A SINGLE POLYPEPTIDE

Tartrate-resistant acid phosphatases have been isolated from a number of sources. These enzymes consists of one subunit (M(r) 30 000-40 000) or two dissimilar subunits (M(r) 15 000-20 000). Previously we isolated the enzyme from human osteoclastomas, as a two-subunit protein. By Northern blotting and hybridization with radiolabelled oligonucleotides corresponding to the N-terminal sequences of the two subunits, we demonstrate here that the enzyme is transcribed as one mRNA which is translated in vitro to produce a single polypeptide of approx. M(r) 33 000. Transcription as a single mRNA species is also the case in other tissues. These results suggest that the osteoclastoma enzyme undergoes post-translational modification in the form of cleavage of a single peptide bond to give a disulphide-bonded two-subunit protein.