Reactions of 1-deaza-FAD-substituted phenol hydroxylase and melilotate hydroxylase.
Year: 1984
Type: article
Abstract: The flavin prosthetic group (FAD) of the aromatic hydroxylases melilotate hydroxylase (EC 1.14.13.4) and phenol hydroxylase (EC 1.14.13.7) was replaced by 1-deaza-FAD (carbon substituted for nitrogen at position 1). Neither modified enzyme could hydroxylate its substrate, both catalyzed the oxidation of NAD(P)H to NAD(P)+ and H2O2. The rate of the reduction of the enzymes by NAD(P)H was increased by the binding of substrate. Both enzymes formed a detectable flavin C(4a) hydroperoxide intermediate upon reaction of the reduced enzyme-substrate complex with oxygen. Reduced 1-deaza-FAD phenol hydroxylase also showed a detectable C(4a) hydroperoxide intermediate when reacted with oxygen in the absence of substrate. The C(4a) hydroperoxide of 1-deaza-FAD phenol hydroxylase, in the absence of phenol, decayed to an intermediate which showed a perturbed oxidized enzyme spectrum, Eox. This intermediate in turn decayed to give the original oxidized enzyme. In the presence of phenol, a second oxidized species with a perturbed spectrum, intermediate X, was apparent after formation of the flavin C(4a) hydroperoxide and before Eox formation. Steady state kinetic analysis of 1-deaza-FAD phenol hydroxylase demonstrated that the Eox to Eox conversion was not in the catalytic cycle. During turnover Eox was reduced by NADPH.
Source: Journal of Biological Chemistry
Authors: K Detmer, L M Schopfer, V Massey
Institution: University of Michigan
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1606089878