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Cyclomaltodextrin glucanotransferase from Bacillus circulans E 192: nitration with tetranitromethane
Author(s) -
Villette JR,
Helbecque N.,
Albani JR,
Sicard PJ,
Bouquelet SJ
Publication year - 1993
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1111/j.1470-8744.1993.tb00240.x
Subject(s) - tetranitromethane , nitration , chemistry , tyrosine , bacillus circulans , residue (chemistry) , enzyme , tryptophan , biochemistry , stereochemistry , organic chemistry , amino acid
Nitration of tyrosine residues was performed on Bacillus circulans E 192 cyclomaltodextrin glucanotransferase (CGTase) using tetranitromethane (TNM). A maximum of 15 out of 28 tyrosine residues is modified with 8 mM TNM, entailing a concomitant loss of enzymic activity and tryptophan fluorescence. Spectroscopic studies suggest that these two phenomena are related to an impairment of the enzyme conformation as a consequence of the tyrosine nitration. The presence of 5 mM acarbose during the CGTase nitration results in the protection of one tyrosine residue and the rate of inactivation is reduced 9.4‐fold. These results support a contribution of a tyrosine residue in the CGTase catalytic site. The nitration of CGTase also entails a decrease in the enzyme's affinity for a beta‐cyclodextrin (beta‐CD) co‐polymer. Kinetic and analytical investigations on isolated modified enzymes support the concept that this phenomenon is unrelated to the modification of tyrosine residues, but rather concerns a side reaction of the reagent occurring at the raw‐starch‐binding site of the CGTase.