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DUAL EFFECTS OF TRYPTOPHAN IN THE HORSERADISH PEROXIDASE SYSTEM THAT GENERATES TRIPLET ACETONE
Author(s) -
Silva Eduardo,
Cilento Giuseppe
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb04157.x
Subject(s) - chemistry , horseradish peroxidase , acetone , tryptophan , peroxidase , hydrogen peroxide , photochemistry , isobutyraldehyde , ternary complex , quenching (fluorescence) , fluorescence , stereochemistry , enzyme , organic chemistry , catalysis , biochemistry , physics , amino acid , quantum mechanics
— When tryptophan is added to the horseradish peroxidase/hydrogen peroxide system, it markedly increases the rate of ‘spontaneous’ conversion of peroxidase‐compound II to the native form without undergoing any alteration by spectral criteria. The D‐isomer is more efficient than the L‐isomer. The latter binds to the enzyme compound II, although at a site not very favourable for reduction. The accelerating effect of tryptophan is also seen when isobutyraldehyde or its enol added to the system, is converted into triplet acetone. Again the D‐isomer is more efficient than the L‐isomer. The D‐isomer is also more efficient in quenching the acetone phosphorescence. These results indicate that, at least in the case of L‐tryptophan where complexation with compound II occurs, the interaction of tryptophan with triplet acetone bound to the enzyme takes place in a ternary complex.