Frederic L. Hoch

Studies on metalloproteins. Soluble zinc-containing protein extracted from human leucocytes☆

Abstract Studies are presented on the purification of soluble zinc-containing proteins from human leucocytes. The criterion for purification is an increase in the zinc to protein ratio, and conditions are defined under which this criterion is valid. Carbonic anhydrase is present in erythrocytes contaminating the leucocytes from which it can be separated by fractional precipitations with ammonium sulfate. This is shown by measurements of carbonic anhydrase activity, zinc, and protein. Further purification of the leucocyte proteins having high zinc to protein ratios was achieved by variations of pH, 11, and ethanol concentration. The maximum zinc to protein ratio attained was 3000 μg. Zn/g. protein. This content of zinc in leucocyte protein is comparable to the magnitude of the metal contents of other metalloproteins.