Dihydrolipoamide dehydrogenase from halophilic archaebacteria: purification and properties of the enzyme from halobacterium halobium
Halophilic archaebacteria possess dihydrolipoamide dehydrogenase activity but apparently lack the 2-oxoacid dehydrogenase multienzyme complexes of which it is usually an integral component. In this paper, the purification of dihydrolipoamide dehydrogenase from Halobacterium halobium is reported. The enzyme is a dimer with a polypeptide chain M/sub r/ of 58,000 (+/-3000). The amino acid composition of the enzyme is compared with those of the eubacterial and eukaryotic dihydrolipoamide dehydrogenases, and evidence is presented to suggest that the N-terminal amino acid of the H. halobium enzyme is blocked. Chemical modification with the trivalent arsenical reagent (p-aminophenyl)dichloroarsine indicates the involvement of a reversibly reducible disulfide bond in the enzyme's catalytic mechanism. The possible metabolic role of this dihydrolipoamide dehydrogenase in the absence of 2-oxoacid dehydrogenase complexes is discussed.
- Research Organization:
- Univ. of Calgary, Alberta (Canada)
- OSTI ID:
- 6583933
- Journal Information:
- Biochemistry; (United States), Vol. 25:13
- Country of Publication:
- United States
- Language:
- English
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