Alkaline phosphatase from human thyroid.
Alkaline phosphatase activity was found in human thyroid homogenate at a specific activity of about 0.01 units/mg protein. The enzyme responsible appears to be a membrane-bound sialoglycoprotein. The properties of thyroid membrane alkaline phosphatase were examined after extraction with non-ionic detergent or butanol. It was detected mainly as a single electrophoretic form with a mobility similar to that of the liver form of the enzyme. It was readily inhibited by homoarginine, but not by phenylalanine. It reacted in Ouchterlony double diffusion with antiserum raised against liver alkaline phosphatase, but not with antiserum to placental alkaline phosphatase. Heat treatment at 56 degree C for 10 min at pH 7.5 resulted in an approx. 50% loss of enzyme activity. Its relative molecular mass was estimated to be 320000 by gel filtration, and 300000 by gradient gel electrophoresis. It required magnesium for full activity, and had a pH optimum of 10.5 in Tris-borate buffers. It was concluded that thyroid alkaline phosphatase belongs to the liver/bone/kidney isoenzyme group, but may exist in a molecular form distinct from others previously described.
D000469:Alkaline Phosphatase / Q000302:isolation & purification / Q000378:metabolism*; D001842:Bone and Bones / Q000201:enzymology; D005260:Female; D006801:Humans; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008970:Molecular Weight; D009928:Organ Specificity; D010920:Placenta / Q000201:enzymology; D011247:Pregnancy; D013347:Subcellular Fractions / Q000201:enzymology; D013961:Thyroid Gland / Q000201:enzymology*
D000469:Alkaline Phosphatase