6-Thiocyanatoflavins and 6-mercaptoflavins as active-site probes of flavoproteins
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6-Thiocyanatoflavins and 6-mercaptoflavins as active-site probes of flavoproteins.
6-Thiocyanatoflavins have been found to be susceptible to nucleophilic displacement reactions with sulfite and thiols, yielding respectively the 6-S-SO3--flavin and 6-mercaptoflavin, with rate constants at pH 7.0, 20 degrees C, of 55 M-1 min-1 for sulfite and 1000 M-1 min-1 for dithiothreitol. The 6-SCN-flavin binds tightly to riboflavin-binding protein as the riboflavin derivative, to apoflavo...
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The chemical reactivity of 8-chloroflavins and 8-mercaptoflavins has been exploited in order to examine the orientation of protein-bound flavins relative to solvent. The apoprotein form of a series of flavoproteins was prepared and the native flavin was replaced by either 8-C1-flavin or 8-mercaptoflavin (FAD, FMN, or riboflavin form as was appropriate). The reconstituted proteins were exposed t...
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Representative examples of the various classes of flavoproteins have been converted to their apoprotein forms and the native flavin replaced by 8-mercapto-FMN or 8-mercapto-FAD. The spectral and catalytic properties of the modified enzymes are characteristically different from one group to another; the results suggest that flavin interactions at positions N(1) or N(5) of the flavin chromophore ...
متن کامل2-Thioflavins as active site probes of flavoproteins.
4-Thioflavins (oxygen at position 4 replaced by sulfur) have been studied as potential active site probes of flavoproteins. They react readily with thiol reagents, with large spectral changes, which should be useful for testing the accessibility of the flavin 4-position in flavoproteins. They have an oxidation-reduction potential at pH 7 of -0.055 V, approximately 0.15 V higher than that of nat...
متن کامل6-Azido- and 6-aminoflavins as active-site probes of flavin enzymes.
6-Azidoflavins have been bound to the apoproteins of five representative flavoproteins and their properties, before and after light irradiation, compared with those of the same proteins containing the appropriate 6-aminoflavin. In the dark the 6-azidoflavoproteins are quite stable, except for L-lactate oxidase, where spontaneous conversion to the 6-amino-FMN enzyme occurs slowly at pH 7. 6-Azid...
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ژورنال
عنوان ژورنال: Biochemistry
سال: 1986
ISSN: 0006-2960,1520-4995
DOI: 10.1021/bi00372a046