Differential substrate behaviour of phenol and aniline derivatives during conversion by horseradish peroxidase.
For the first time saturating overall k(cat) values for horseradish peroxidase (HRP) catalysed conversion of phenols and anilines are described. These k(cat) values correlate quantitatively with calculated ionisation potentials of the substrates. The correlations for the phenols are shifted to higher k(cat) values at similar ionisation potentials as compared to those for anilines. (1)H-NMR T(1) relaxation studies, using 3-methylphenol and 3-methylaniline as the model substrates, revealed smaller average distances of the phenol than of the aniline protons to the paramagnetic Fe(3+) centre in HRP. This observation, together with a possibly higher extent of deprotonation of the phenols than of the anilines upon binding to the active site of HRP, may contribute to the relatively higher HRP catalysed conversion rates of phenols than of anilines.
Van Haandel
M J
MJ
Department of Biomolecular Sciences, Laboratory of Biochemistry, Agricultural University, Dreijenlaan 3, 6703 HA, Wageningen, The Netherlands.
Claassens
M M
MM
Van der Hout
N
N
Boersma
M G
MG
Vervoort
J
J
Rietjens
I M
IM
D000814:Aniline Compounds / Q000737:chemistry*; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D003201:Computers; D006735:Horseradish Peroxidase / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D000814:Aniline Compounds; D010636:Phenols; D006735:Horseradish Peroxidase; C021313:methylaniline