Kinetics of reduction of metmyoglobins by ascorbate. Effect of the modification of the heme distal side, heme propionates, and 2,4-substituents of deuterohemin
Rate constants are reported for the reduction by ascorbate of BrCN-modified metmyoglobin and metmyoglobin reconstituted with 2,4-disubstituted deuterohemin and with protohemin dimethyl ester. Modification of the heme distal histidylimidazole by cyanogen bromide and of the heme propionates to their methyl esters accelerated the reduction rate compared with that for its native form, suggesting that the structural change in the iron site from hexa- to pentacoordination is an important factor. The logarithm of the second-order rate constants for the reduction of the metmyoglobin reconstituted with a 2,4-disubstituted deuterohemin (-CHO, -COC/sub 2/H/sub 5/, -COCH/sub 3/, -CH=CH/sub 2/, and -H) is linearly correlated with the pK/sub 3/ of the acid-dissociation constants of the porphyrin monocation. This suggests that the electron factor is predominant for these substituents. Mesohemin reconstituted myoglobin is an exception, perhaps for steric reasons. 41 references, 3 figures, 3 tables.
- Research Organization:
- Shimane Univ., Matsue, Japan
- OSTI ID:
- 6917428
- Journal Information:
- Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 25:26; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ASCORBIC ACID
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CYANIDES
DATA
DEUTERIUM
ENZYME ACTIVITY
EXPERIMENTAL DATA
GLOBIN
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MYOGLOBIN
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
REDUCTION
SALTS
STABLE ISOTOPES
TRACER TECHNIQUES
VITAMINS