Purification of human placental alkaline phosphatase. Salt effects in affinity chromatography

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Abstract
Human placental alkaline phosphatase was chromatographed on Sepharose derivatives of d- and l-phenylalanine, l-leucine, glycine, aniline and p-aminobenzoic acid in high concentrations of (NH4)2SO4. Retention on these columns was greatest at the highest concentrations of (NH4)2SO4. By using decreasing concentrations and changing the types of salts, elution was effected from each of the columns. The (NH4)2SO4-mediated retention appeared to be related to the hydrophobic character of the substituted Sepharose, rather than to any specific binding site of the enzyme. It is suggested that this provides a way of controlling hydrophobic affinity chromatography. By use of chromatography on l-phenylalanine–Sepharose and of DEAE-Sephadex chromatography in the presence of Triton X-100 detergent, a preparation of highly purified (1000-fold) human placental alkaline phosphatase was obtained in 22% yield.