Persistently raised serum acid phosphatase activity in a patient with hypophosphatasia: electrophoretic and molecular weight characterisation as type 5.
Hypophosphatasia is a rare disorder characterised by low levels of serum alkaline phosphatase activity resulting in abnormal phosphorylated metabolites and varying skeletal abnormality. We have followed a patient with adult type hypophosphatasia for over ten years who has also shown a persistently elevated tartrate resistant acid phosphatase activity (TRAP) without any obvious cause. Characterisation of this TRAP by polyacrylamide gel electrophoresis (pH 4.0) showed migration to band 5 position. Molecular weight determination by FPLC and an estimate of the molecular weight by gradient gel electrophoresis gave a molecular weight of 29,000-43,600. This molecular weight makes it unlikely for this to be a IgG/TRAP complex persisting in the circulation. Paranitrophenylphosphate was the preferred substrate. This characterises the enzyme as type 5 acid phosphatase which is of the mononuclear/phagocyte type, possibility of osteoclastic origin, though the tissue source remains unknown.
Iqbal
S J
SJ
Department of Chemical Pathology, Leicester Royal Infirmary, UK. SJI@le.ac.uk
D000135:Acid Phosphatase / Q000097:blood*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007014:Hypophosphatasia / Q000097:blood / Q000201:enzymology*; D007527:Isoenzymes / Q000097:blood*; D007700:Kinetics; D008875:Middle Aged; D008970:Molecular Weight; D000071681:Tartrate-Resistant Acid Phosphatase
D007527:Isoenzymes; D000135:Acid Phosphatase; D000071681:Tartrate-Resistant Acid Phosphatase