Journal of Biochemistry Advance Access originally published online on August 30, 2007
Journal of Biochemistry 2007 142(4):453-458; doi:10.1093/jb/mvm159
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© 2007 The Japanese Biochemical Society.
Haeme-regulated Degradation of
-Aminolevulinate Synthase 1 in Rat Liver Mitochondria
1Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, 812-8581, Japan; and 2Department of Biochemistry, School of Medicine, Kinki University, 377-2 Ohno-Higashi, Osaka-Sayama, 589-8511, Japan
*To whom correspondence should be addressed. Tel: +81-92-642-2601, Fax: +81-91-642-2607, E-mail: taogiscc{at}mbox.nc.kyushu-u.ac.jp
Received May 2, 2007; Accepted June 26, 2007
| Abstract |
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Protein turnover, which occurs at various rates, is critical for the homeostasis of cellular protein levels. However, the proteolysis systems that determine the turnover rate of mitochondrial proteins are largely unknown. Delta-aminolevulinic acid synthase (ALAS) 1, a rate-limiting enzyme in the haeme biosynthesis, is one of the mitochondrial proteins that have a very short lifetime. In this study, to reveal the regulatory mechanisms for ALAS1 degradation, we examined the turnover rates of ALAS1 in rat liver under several conditions. In primary rat hepatocytes, the degradation of ALAS1 was stimulated by haeme, and suppressed by inhibition of haeme biosynthesis. Furthermore, the haeme-stimulated degradation of ALAS1 was observed in the isolated mitochondria. These results suggested that, in mitochondria, there exists an ALAS1 degradation system that is regulated by cellular haeme level and plays a crucial role in the regulation of haeme biosynthesis.
Key Words: ALAS1, haeme and metabolism, metabolic regulation, mitochondria, protein degradation
Abbreviations:
ALAS,
-aminolevulinic acid synthase; Bt2cAMP, dibutyryladenosine 3',5'-cyclic monophosphate; CHI, cycloheximide; DDC, 3,5-dicarbethoxy-1,4-dihydrocollidine; MSH, mannitol–sucrose–Hepes; PB, phenobarbital; SA, succinylacetone; TOM40, translocase of outer membrane
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