Leucine Aminopeptidase from Swine Kidney: Purification, Molecular Weight, Subunit, and Amino Acid Composition

A homogeneous leucine aminopeptidase was obtained from mixed breed swine kidneys by means of chromatography on a special column. After coupling an inhibitor, N-sulfanilyl N'-butylcarbamide, to Sepharose 6B, the derivative did not absorb the enzyme, but absorbed a non-enzymatically active protein. The enzyme showed a single band on disc-gel electrophoresis. The molecular weight of the enzyme has 320,000 daltons. In 6 M guanidine solution containing 0.5% 2-mercaptoethanol at pH 8, the enzyme exhibited a molecular weight of 53,000 on equilibrium centrifugation. A similar value, 54,000, for the subunit of the enzyme was found on SDS-gel electrophoresis. The amino acid composition of the enzyme is also reported.