Cargando…
THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES
Two isozymes of aspartate aminotransferase have been demonstrated biochemically. One isozyme is found in the mitochondrial fraction of the cytoplasm, the other ("soluble") in the supernatant. Both isozymes can be demonstrated by the cytochemical technique of Lee and Torack, as reported in...
Autores principales: | , |
---|---|
Formato: | Texto |
Lenguaje: | English |
Publicado: |
The Rockefeller University Press
1970
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2108396/ https://www.ncbi.nlm.nih.gov/pubmed/5535135 |
_version_ | 1782139041159839744 |
---|---|
author | Papadimitriou, J. M. Van Duijn, P. |
author_facet | Papadimitriou, J. M. Van Duijn, P. |
author_sort | Papadimitriou, J. M. |
collection | PubMed |
description | Two isozymes of aspartate aminotransferase have been demonstrated biochemically. One isozyme is found in the mitochondrial fraction of the cytoplasm, the other ("soluble") in the supernatant. Both isozymes can be demonstrated by the cytochemical technique of Lee and Torack, as reported in the preceding report. Aldehyde fixation rapidly inactivates both isozymes, especially the soluble one. Inactivation can be delayed by addition of ketoglutarate to the fixative. The ketoglutarate probably competes with the fixative for the active site of the enzyme, thus protecting that region of the molecule. This enables adequate tissue preservation with enough remaining enzymatic activity to be demonstrated by the precipitation of oxaloacetate as the lead salt from a medium containing α-ketoglutaric acid aspartic acid, and lead nitrate. Electron-opaque material was found not only in mitochondria but, as the result of substrate protection, on the plasma membranes of many cells including erythrocytes and bacteria, the limiting membrane of peroxisomes, and the transverse tubular system of striated muscle. Occasional centrioles, neurotubules, tubules in the tails of spermatozoa, the A-I band junction in myofibrils of striated muscle, and the ground substance between cisternae of endoplasmic reticulum in intestinal goblet cells also showed precipitate. In all cases, replacement of L-aspartic acid by D-aspartic acid in the medium resulted in unstained sections. The sensitivity of extramitochondrial sites to fixation, the need of ketoglutarate as an agent for protecting the enzymatic activity during the fixation process, and the known presence of only soluble isozyme in erythrocytes indicate that enzymatic activity at these sites can be attributed to the soluble isozyme. Localization of the soluble isozyme on the plasma membrane may be related to possible involvement in depolarization phenomena, amino acid transport, or synthesis of plasma membrane-bound mucopolysaccharides. |
format | Text |
id | pubmed-2108396 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 1970 |
publisher | The Rockefeller University Press |
record_format | MEDLINE/PubMed |
spelling | pubmed-21083962008-05-01 THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES Papadimitriou, J. M. Van Duijn, P. J Cell Biol Article Two isozymes of aspartate aminotransferase have been demonstrated biochemically. One isozyme is found in the mitochondrial fraction of the cytoplasm, the other ("soluble") in the supernatant. Both isozymes can be demonstrated by the cytochemical technique of Lee and Torack, as reported in the preceding report. Aldehyde fixation rapidly inactivates both isozymes, especially the soluble one. Inactivation can be delayed by addition of ketoglutarate to the fixative. The ketoglutarate probably competes with the fixative for the active site of the enzyme, thus protecting that region of the molecule. This enables adequate tissue preservation with enough remaining enzymatic activity to be demonstrated by the precipitation of oxaloacetate as the lead salt from a medium containing α-ketoglutaric acid aspartic acid, and lead nitrate. Electron-opaque material was found not only in mitochondria but, as the result of substrate protection, on the plasma membranes of many cells including erythrocytes and bacteria, the limiting membrane of peroxisomes, and the transverse tubular system of striated muscle. Occasional centrioles, neurotubules, tubules in the tails of spermatozoa, the A-I band junction in myofibrils of striated muscle, and the ground substance between cisternae of endoplasmic reticulum in intestinal goblet cells also showed precipitate. In all cases, replacement of L-aspartic acid by D-aspartic acid in the medium resulted in unstained sections. The sensitivity of extramitochondrial sites to fixation, the need of ketoglutarate as an agent for protecting the enzymatic activity during the fixation process, and the known presence of only soluble isozyme in erythrocytes indicate that enzymatic activity at these sites can be attributed to the soluble isozyme. Localization of the soluble isozyme on the plasma membrane may be related to possible involvement in depolarization phenomena, amino acid transport, or synthesis of plasma membrane-bound mucopolysaccharides. The Rockefeller University Press 1970-10-01 /pmc/articles/PMC2108396/ /pubmed/5535135 Text en Copyright © 1970 by The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/). |
spellingShingle | Article Papadimitriou, J. M. Van Duijn, P. THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES |
title | THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES |
title_full | THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES |
title_fullStr | THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES |
title_full_unstemmed | THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES |
title_short | THE ULTRASTRUCTURAL LOCALIZATION OF THE ISOZYMES OF ASPARTATE AMINOTRANSFERASE IN MURINE TISSUES |
title_sort | ultrastructural localization of the isozymes of aspartate aminotransferase in murine tissues |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2108396/ https://www.ncbi.nlm.nih.gov/pubmed/5535135 |
work_keys_str_mv | AT papadimitrioujm theultrastructurallocalizationoftheisozymesofaspartateaminotransferaseinmurinetissues AT vanduijnp theultrastructurallocalizationoftheisozymesofaspartateaminotransferaseinmurinetissues AT papadimitrioujm ultrastructurallocalizationoftheisozymesofaspartateaminotransferaseinmurinetissues AT vanduijnp ultrastructurallocalizationoftheisozymesofaspartateaminotransferaseinmurinetissues |