Purification and characterization of thiol aminopeptidase from the cytosolic fraction of human placenta.
A thiol-dependent aminopeptidase was purified from the cytosolic fraction of human placenta. The purified enzyme consisted of a single polypeptide chain with a mol wt of 95,000. The enzyme was most active in the neutral region with Ala-pNA as substrate, and the activity was increased about 20-fold in the presence of some -SH compounds. The results of substrate specificity studies indicated that the enzyme hydrolyzes bonds involving the amino groups of neutral and basic amino acid residues. However, higher thiol-dependent activity was only detected with neutral ones. The enzyme was strongly inhibited by microbial aminopeptidase inhibitors, puromycin, o-phenanthroline, and sulfhydryl reactive-reagents. As to several naturally occurring peptides tested, the enzyme showed N-terminal Tyr-releasing activity toward enkephalins and kinin-converting activity.
D000626:Aminopeptidases / Q000302:isolation & purification* / Q000502:physiology; D002848:Chromatography, DEAE-Cellulose; D003600:Cytosol / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D010920:Placenta / Q000201:enzymology / Q000648:ultrastructure*; D011247:Pregnancy; D011480:Protease Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity
D011480:Protease Inhibitors; D000626:Aminopeptidases; C036008:aminopeptidase, sulfhydryl dependent