Intestinal‐like alkaline phosphatase expressed in normal human adult kidney

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Abstract
Human adult kidney was found to contain not only the ‘tissue‐unspecific alkaline phosphatase’ but also another alkaline phosphatase isozyme. By use of monoclonal antibodies specific for human intestinal alkaline phosphatase, this kidney isozyme was purified to homogeneity by immunoaffinity chromatography. The structural and kinetic properties of the enzyme were compared with those of the other alkaline phosphatase isozymes expressed in normal human tissues, i.e. the placental, intestinal, meconial (fetal), liver and kidney isozymes. The new kidney isozyme was clearly different from both the tissue‐unspecific and the adult intestinal alkaline phosphatase as regards isoelectric point, molecular mass and peptide maps after cyanogen bromide cleavage, but it was found to be identical to the meconial alkaline phosphatase. The results demonstrate simultaneous expression of two alkaline phosphatase isozymes in human kidney, one of which is normally related only to the fetal intestine.