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In vitro and in vivo studies on the degradation of metallothionein.

Degradation of metallothionein (MT) from rat liver was examined. Degradation of apo-MT by liver homogenate was greater than that by cytosol. At pH 5.5, degradation by homogenate was more than that at pH 7.2. These findings suggest that proteases that function at acidic pH are probably involved in MT...

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Autores principales: Klaassen, C D, Choudhuri, S, McKim, J M, Lehman-McKeeman, L D, Kershaw, W C
Formato: Texto
Lenguaje:English
Publicado: 1994
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1567434/
https://www.ncbi.nlm.nih.gov/pubmed/7843089
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author Klaassen, C D
Choudhuri, S
McKim, J M
Lehman-McKeeman, L D
Kershaw, W C
author_facet Klaassen, C D
Choudhuri, S
McKim, J M
Lehman-McKeeman, L D
Kershaw, W C
author_sort Klaassen, C D
collection PubMed
description Degradation of metallothionein (MT) from rat liver was examined. Degradation of apo-MT by liver homogenate was greater than that by cytosol. At pH 5.5, degradation by homogenate was more than that at pH 7.2. These findings suggest that proteases that function at acidic pH are probably involved in MT degradation. Because lysosomes are the principal subcellular organelles that contain acid proteases (cathepsins), we compared the degradation of apo-MT by lysosomes and cytosol. Apo-MT was degraded about 400 times faster by lysosomal fraction than by cytosolic fraction. To determine the relative importance of different cathepsins, we used different inhibitors. Leupeptin, which inhibits cathepsins B and L, inhibited the degradation of apo-MT by 80%, implying that cathepsins B and/or L might be very important in the intracellular turnover of MT. Cathepsin D appeared to be the least significant, because apo-MT degradation was reduced by about 20% by inhibiting cathepsin D. When we extended this study with purified cathepsins, we obtained the same answer, i.e., the ability of different cathepsins to degrade apo-MT was in the following order: cathepsin B >> cathepsin C > cathepsin D. While apo-MT was susceptible to degradation, ZnMT and CdMT were highly resistant to degradation. Coincubation of ZnMT or CdMT with either lysosomal extract or purified cathepsins did not result in any appreciable degradation even after 16 hr. However, longer incubations did result in some degradation, especially by purified cathepsin B. Interestingly, CdMT degraded little faster than ZnMT by both lysosomal extract as well as purified cathepsin B.(ABSTRACT TRUNCATED AT 250 WORDS)
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spelling pubmed-15674342006-09-19 In vitro and in vivo studies on the degradation of metallothionein. Klaassen, C D Choudhuri, S McKim, J M Lehman-McKeeman, L D Kershaw, W C Environ Health Perspect Research Article Degradation of metallothionein (MT) from rat liver was examined. Degradation of apo-MT by liver homogenate was greater than that by cytosol. At pH 5.5, degradation by homogenate was more than that at pH 7.2. These findings suggest that proteases that function at acidic pH are probably involved in MT degradation. Because lysosomes are the principal subcellular organelles that contain acid proteases (cathepsins), we compared the degradation of apo-MT by lysosomes and cytosol. Apo-MT was degraded about 400 times faster by lysosomal fraction than by cytosolic fraction. To determine the relative importance of different cathepsins, we used different inhibitors. Leupeptin, which inhibits cathepsins B and L, inhibited the degradation of apo-MT by 80%, implying that cathepsins B and/or L might be very important in the intracellular turnover of MT. Cathepsin D appeared to be the least significant, because apo-MT degradation was reduced by about 20% by inhibiting cathepsin D. When we extended this study with purified cathepsins, we obtained the same answer, i.e., the ability of different cathepsins to degrade apo-MT was in the following order: cathepsin B >> cathepsin C > cathepsin D. While apo-MT was susceptible to degradation, ZnMT and CdMT were highly resistant to degradation. Coincubation of ZnMT or CdMT with either lysosomal extract or purified cathepsins did not result in any appreciable degradation even after 16 hr. However, longer incubations did result in some degradation, especially by purified cathepsin B. Interestingly, CdMT degraded little faster than ZnMT by both lysosomal extract as well as purified cathepsin B.(ABSTRACT TRUNCATED AT 250 WORDS) 1994-09 /pmc/articles/PMC1567434/ /pubmed/7843089 Text en
spellingShingle Research Article
Klaassen, C D
Choudhuri, S
McKim, J M
Lehman-McKeeman, L D
Kershaw, W C
In vitro and in vivo studies on the degradation of metallothionein.
title In vitro and in vivo studies on the degradation of metallothionein.
title_full In vitro and in vivo studies on the degradation of metallothionein.
title_fullStr In vitro and in vivo studies on the degradation of metallothionein.
title_full_unstemmed In vitro and in vivo studies on the degradation of metallothionein.
title_short In vitro and in vivo studies on the degradation of metallothionein.
title_sort in vitro and in vivo studies on the degradation of metallothionein.
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1567434/
https://www.ncbi.nlm.nih.gov/pubmed/7843089
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