Distribution of neutral endopeptidase activity in human blood leukocytes.
We investigated the distribution of neutral endopeptidase (NEP; EC 3.4.24.11) activity, a possible regulatory enzyme for neuropeptide-induced leukocyte activations, in each cell type of human blood leukocytes. The NEP activity assessed by an NEP inhibitor phosphoramidon-sensitive Met5-enkephalin degrading activity was present in neutrophils and the common acute lymphoblastic leukemia antigen (CALLA)-positive leukemic cells (59 pmol/min/10(6) cells and 62 pmol/min/10(6) cells, respectively); however, the NEP activity was virtually absent in lymphocytes, monocytes, eosinophils, basophils, CALLA-negative leukemic cells, or a promyelocytic cell line HL-60. The enzymatic activity was characterized as NEP on the basis of the values of kinetic parameters (Km = 61 microM, Kcat = 1,692 min-1, and Kcat/Km = 28 min-1 microM-1) and the values of IC50 of two NEP inhibitors phosphoramidon and thiorphan (7.4 nM and 8.4 nM, respectively). The distribution of NEP detected immunocytochemically using anti-NEP monoclonal antibodies was also found to be parallel with the distribution of NEP activity among peripheral blood leukocytes.
Iwamoto
I
I
Second Department of Internal Medicine, Chiba University School of Medicine, Japan.
Kimura
A
A
Ochiai
K
K
Tomioka
H
H
Yoshida
S
S
D001491:Basophils / Q000201:enzymology; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D002469:Cell Separation / Q000379:methods; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D004804:Eosinophils / Q000201:enzymology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000097:blood / Q000201:enzymology; D007962:Leukocytes / Q000166:cytology / Q000201:enzymology*; D015260:Neprilysin / Q000097:blood* / Q000302:isolation & purification; D009504:Neutrophils / Q000201:enzymology; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000097:blood / Q000201:enzymology
D015260:Neprilysin