Identification of essential amino-acid residues in Azotobacter vinelandii isocitrate dehydrogenase by radical anions and H atoms
- Hope Coll., Holland, MI
Pure TPN/sup +/-specific isocitrate dehydrogenase from Azotobacter vinelandii was irradiated with H atoms generated in a ..gamma..-irradiated solution at pH 6.5. A G(-activity) = 0.12 +- 0.01 was found. At the same time no corresponding loss in free sulfhydryls was observed. These results confirmed the essentiality of methionine for the enzymatic activity as known from previous studies. Irradiation with the radical anions, (CNS)/sub 2/- and Br/sub 2//sup -/ generated in ..gamma..-irradiated solutions at pH 6.5, strongly inactivated isocitrate dehydrogenase with yields of G(-activity) of 2.1 and 3.9, respectively. Part of the inactivating effect, however, is due to oxidation of sulfhydryl groups. These results lead to the conclusion that tryptophan is an essential amino-acid residue to isocitrate dehydrogenase from A. vinelandii. The presence of tryptophan in the enzyme was demonstrated by pulse radiolysis.
- OSTI ID:
- 5341643
- Journal Information:
- Radiat. Res.; (United States), Vol. 80:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
DEHYDROGENASES
BIOCHEMICAL REACTION KINETICS
GAMMA RADIATION
BIOLOGICAL RADIATION EFFECTS
AZOTOBACTER
CATALYSIS
DOSE-RESPONSE RELATIONSHIPS
ENZYME INHIBITORS
EXPERIMENTAL DATA
ISOLATED VALUES
METABOLISM
QUALITATIVE CHEMICAL ANALYSIS
TRYPTOPHAN
AMINO ACIDS
AZOLES
BACTERIA
BIOLOGICAL EFFECTS
CARBOXYLIC ACIDS
CHEMICAL ANALYSIS
DATA
DATA FORMS
ELECTROMAGNETIC RADIATION
ENZYMES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INDOLES
INFORMATION
IONIZING RADIATIONS
KINETICS
MICROORGANISMS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDOREDUCTASES
PYRROLES
RADIATION EFFECTS
RADIATIONS
REACTION KINETICS
560111* - Radiation Effects on Biochemicals- In Vitro- (-1987)
550200 - Biochemistry