Aminotripeptidase from Human Plasma
1982 Volume 11 Issue 4 Pages 314-323
Details
1982 Volume 11 Issue 4 Pages 314-323
L-Leucylglycylglycine hydrolyzing aminopeptidase was electrophoretically shown to be present in human serum using the leucine dehydrogenase coupled staining technique. Before investigating the clinical significances of this enzyme, it was partially purified from normal human plasma by ammonium sulfate fractionation, column chromatography on DEAEcellulose, gel filtration on a Sephadex G-100, and preparative isoelectric focusing.
The molecular weight of the enzyme was estimated to be 56,000 by gel filtration on a Sephadex G-75, and the isoelectric point of the enzyme was pH 5.01 by isoelectric focusing. This enzyme specifically hydrolyzes tripeptides, such as L-leucylglycine and L-valylglycine, at am inoterminals of peptides. Moreover, the enzyme does not act on dipeptides and amino acid amides. The enzyme is slightly inhibited by EDTA, EGTA and HEDTA, and strongly by o-phenanthroline. Bestatin, di-L-leucine and tri-L-leucine competitively inhibit the enzyme, and the inhibition constants were estimated to be 0.18×10-6, for bestatin, 70×10-6, for di-Lleucine, and 6.0×10-6 mole/liter for tri-L-leucine. These physical and kinetic properties closely resemble those of aminotripeptidase (Tripeptide aminopetidase, EC 3.4.11.4) obtained from monkey brain and swine kidney.
