Possible action of human placental aminopeptidase N in feto-placental unit.
Aminopeptidase N purified from human placenta actively hydrolyzed various immunomodulating peptides from their N-terminus such as splenopentin, thymopentin, thymic humoral factor gamma 2, tuftsin and rigin in vitro. Aminopeptidase N also actively hydrolyzed neuropeptide hormones (met-enkephalin, somatostatin and neurokinin A) and vasoactive peptides (lysyl-bradykinin and angiotensin III) from their N-terminus. In addition, angiotensin II, secretin, thymopoietin II peptide fragment, motilin, endothelin-I and insulin were tested for hydrolysis by aminopeptidase N. Km and Vmax values for the N-terminal amino acid, Thr, a liberation from tuftsin were 267 microM and 8.33 mumol/min/mg protein, respectively. L-Leucyl-p-nitroanilidase activity in the human placental membrane fraction was almost completely neutralized by anti-aminopeptidase N antibody. Our present study suggests that possible roles for surface enzyme aminopeptidase N in the human placenta would be to down-regulate the action of immunomodulating peptides as well as vasoactive and neuropeptide hormones, and to control both immunology and endocrinology of pregnancy.
Mizutani
S
S
Department of Obstetrics and Gynecology, Nagoya University School of Medicine, Japan.
Goto
K
K
Nomura
S
S
Ino
K
K
Goto
S
S
Kikkawa
F
F
Kurauchi
O
O
Goldstein
G
G
Tomoda
Y
Y
D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000302:isolation & purification / Q000502:physiology*; D000818:Animals; D018826:CD13 Antigens; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D015536:Down-Regulation; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005326:Fetal Proteins / Q000502:physiology*; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010920:Placenta / Q000737:chemistry / Q000502:physiology*; D011247:Pregnancy; D011817:Rabbits
D005326:Fetal Proteins; D009479:Neuropeptides; D009842:Oligopeptides; D010446:Peptide Fragments; D000626:Aminopeptidases; D018826:CD13 Antigens