Localization Of Leucine Aminopeptidase Research Articles

Immunohistochemical and cytochemical evidences for a possible localization of leucine aminopeptidase in the Merkel cell granule

Localization of leucine aminopeptidase (LAP) in the Merkel cell-axon complex was studied immunohistochemically and cytochemically in the labial tissues of the mouse, rat, dog, and monkey. Anti-LAP was obtained in rabbits by the injection of commercially supplied swine LAP which was confirmed as electrophoretically pure. The Merkel cells of the mouse, rat, and monkey were positively stained by treatment with anti-LAP but the Merkel cells of the dog were negative. When ultrathin sections of the hair follicle from the rat whisker pad, which contain an abundance of Merkel cells, were processed by immuno-peroxidase or by the immuno-gold method, the reaction products were predominantly deposited on the Merkel cells granules. Furthermore, an immuno-blot assay revealed that an extract of the hair follicles from murine whisker pads contained a molecule of relative molecular mass Mr = 60,000 which is similar in size to a subunit of swine LAP. Thus, it appears that Merkel cell granules of rodents and the monkey contain a protein which resembles lucine aminopeptidase.

Localization of leucine aminopeptidase and vitamin B-12 binding protein in rabbit peripheral blood polymorphonuclear leukocytes

Polymorphonuclear leukocytes were isolated from the peripheral blood of rabbits by Ficoll-Hypaque centrifugation followed by dextran sedimentation. The granulocytes were homogenized in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density gradient centrifugation. Leucine aminopeptidase, when assayed with L-leucine-7-amido-4-methyl-coumarin as substrate, showed a similar distribution to N-acetyl- ß-glucosaminidase and thus is localized to the tertiary granules. There was no leucine aminopeptidase associated with the plasma membrane of these cells. Further experiments with purified plasma membranes and inhibitor studies using diazotized sulphanilic acid further confirmed that leucine aminopeptidase had a purely intracellular localization. Vitamin B-12 binding protein showed a similar localization to alkaline phosphatase indicating that, as in human polymorphonuclear leukocytes, vitamin B-12 binding protein is located to the specific granules.

Subcellular localization of leucine aminopeptidase in rabbit polymorphonuclear leucocytes

Subcellular localization of leucine aminopeptidase in rabbit polymorphonuclear leucocytes

NEW OBSERVATIONS ON DISCREPANCIES IN THE HISTOCHEMICAL LOCALIZATION OF LEUCINE AMINOPEPTIDASE

Differences in the localization of leucine aminopeptidase in the cortex of the rat kidney have been reported with two methods employing the same substrate. Test tube and tissue experiments were carried out in an effort to explain the disparity. Substrate concentration, pH, buffer, the use of an activator, duration of incubation and temperature of incubation were found to have insignificant effects. Four important findings were (1) leucine aminopeptidase activity of the inner cortex of the rat kidney assayed two to three times greater than that of the outer cortex, (2) this difference was confirmed by histochemical demonstration with both methods, (3) fast blue B inhibited the enzyme more than fast garnet GBC and fast Corinth V, and (4) fast blue B coupled faster than the other diazonium salts.