Differential expression of monomeric and proteolytically processed forms of tartrate-resistant acid phosphatase in rat tissues.
Purple acid phosphatase (PAP), also known as tartrate-resistant acid phosphatase (TRAP), uteroferrin or type 5 acid phosphatase (Acp5) is synthesized as an N-glycosylated monomeric latent precursor, which can be processed by limited proteolysis to a disulfide-linked two-subunit form with increased enzyme activity. In this study, we disclosed that the proteolytically processed two-subunit form constitutes the major PAP/TRAP variant in monocytic cells in spleen, thymus, liver and colon. In addition significant expression of the monomeric PAP/TRAP, indicating a non-enzymatic function, was detected in epithelial cells of colon, lung and kidney. Interestingly, proteolytic processing alone did not activate the enzyme but rendered the enzyme more susceptible to activation by reductants. Thus, beside limited proteolysis, the subcellular redox state could also be a determinant of enzyme action in vivo. The co-localization of PAP/TRAP and the cysteine protease cathepsin L could suggest a role for cathepsin L in the in vivo proteolytic processing of PAP/TRAP in monocytic cells.
Lång
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Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, F46 Karolinska University Hospital, 141 86 Stockholm, Sweden.
Andersson
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D000135:Acid Phosphatase / Q000378:metabolism*; D000818:Animals; D056657:Cathepsin K; D056668:Cathepsin L; D002403:Cathepsins / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D019281:Dimerization; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism*; D009928:Organ Specificity; D010084:Oxidation-Reduction; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000071681:Tartrate-Resistant Acid Phosphatase
D007527:Isoenzymes; D021122:Protein Subunits; D012333:RNA, Messenger; D000135:Acid Phosphatase; C000605512:Acp5 protein, rat; D000071681:Tartrate-Resistant Acid Phosphatase; D002403:Cathepsins; D003546:Cysteine Endopeptidases; D056668:Cathepsin L; C534280:Ctsl protein, rat; D056657:Cathepsin K; C534133:Ctsk protein, rat