A Conjugated Form of Aminopeptidase From Autolyzed Extracts of Kidney Tissue

Peptidase-rich fractions were prepared from autolyzed extracts of pig kidney. These preparations showed many properties in common with leucine aminopeptidase but exhibited remarkable stability when subjected to vigorous emulsification with chloroform–octanol. By chromatography on DEAE-cellulose and on Sephadex gel under appropriate conditions, it was demonstrated that the aminopeptidase in these preparations exists in a conjugated form which is dissociable into an enzymatically-active protein moiety and inactive fractions containing nucleic acid. The dissociated form of the enzyme is extremely labile and shows an A[280/260] ratio of 1.2. Starch gel electrophoresis of the purified enzyme fraction shows several enzymatically-active protein bands and only traces of inactive protein. Preliminary evidence suggests that the aminopeptidase present in the supernatant fraction of non-autolyzed homogenates of kidney tissue exists also in a protected conjugated form.