Abstract:
:We partially purified a preparation from Escherichia coli that proteolytically degrades the enzyme glutamine synthetase [L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2]. The degradation is at least a two-step process. First, the glutamine synthetase undergoes an oxidative modification. This modification leads to loss of catalytic activity and also renders the protein susceptible to proteolytic attack in the second step. The oxidative step displays characteristics of a mixed-function oxidation, requiring both molecular oxygen and a reduced nucleotide. This step can also be catalyzed by a purified, mammalian cytochrome P-450 system, as well as by a model system consisting of ascorbic acid and oxygen. Catalase blocks this oxidative modification step. Thus, the overall process of proteolytic degradation can be observed only if care is taken to remove catalase activity from the extracts. The inactivation reaction is dependent on the state of adenylylation of the glutamine synthetase, suggesting that this a physiologically important reaction. If so, then mixed-function oxidases are now implicated in the process of intracellular protein turnover.
journal_name
Proc Natl Acad Sci U S Aauthors
Levine RL,Oliver CN,Fulks RM,Stadtman ERdoi
10.1073/pnas.78.4.2120subject
Has Abstractpub_date
1981-04-01 00:00:00pages
2120-4issue
4eissn
0027-8424issn
1091-6490journal_volume
78pub_type
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