Human kidney l-arginine:glycine amidinotransferase (transamidinase) has been purified to a homogeneous state as defined by native and sodium dodecyl sulfate gel electrophoresis and by ultracentrifugation (sedimentation equilibrium) experiments. The four steps in the isolation procedure were chromatography with DEAE-cellulose, gel filtration with Sephadex G-150, chromatography with phenyl Sepharose, and high-pressure liquid chromatography with hydroxylapatite. The final product represented a 90-fold purification of the enzyme. Human kidney transamidinase is a dimer with a molecular mass of 89,000 Da and subunit masses of 44,000 Da. The Km for arginine and glycine were both 2.5 mm and the Vmax was 0.5 μmol ornithine/min/mg protein. The ultraviolet absorption spectrum, specific activity, and isoelectric points were determined for human kidney transamidinase. Multiple forms of the enzyme were obtained by isoelectric focusing. Human kidney transamidinase cross-reacted with polyclonal antibodies raised to rat kidney transamidinase. All of the properties of human kidney transamidinase that we have examined were similar to those of rat kidney transamidinase. A close evolutionary relationship between the rat and human kidney transamidinase is suggested.
Bibliographical noteFunding Information:
’ This work was supported by Grant AM 26505 from the National Institutes of Health. ’ Data in this report are from the dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy in the Graduate College of the University of Minnesota. ’ Present address: Endocrinology Unit, Mayo Clinic, St. Mary’s Hospital, Rochester, Minn. 55901. 4 To whom correspondence should be addressed at Department of Biochemistry, 4-225 Millard Hall, University of Minnesota, Minneapolis, Minx 55455.
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