Open Access2‐Aminobenzoyl‐CoA monooxygenase/reductase, a novel type of flavoenzyme
Author(s) -
BUDER Reiner,
ZIEGLER Klaus,
FUCHS Georg,
LANGKAU Bernd,
GHISLA Sandro
Publication year - 1989
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1989.tb15160.x
Subject(s) - sodium borohydride , chemistry , decarboxylation , reductase , thioester , cofactor , coenzyme a , monooxygenase , stereochemistry , flavin group , transamination , enzyme , organic chemistry , medicinal chemistry , catalysis , cytochrome p450
The reaction catalyzed by 2‐aminobenzoyl‐coenzyme‐A monooxygenase/reductase from a denitrifying Pseudomonas sp. has been investigated. 2‐Aminobenzoyl‐CoA and 2‐amino[ carboxy‐ 14 C]benzoyl‐CoA were synthesized enzymatically using 2‐aminobenzoyl‐CoA synthetase from the same organism. The product was purified by chromatography and characterized by ultraviolet/visible and 1 H‐NMR spectroscopy. The conversion of 2‐aminobenzoyl‐CoA catalyzed by the monooxygenase/reductase requires NADH and oxygen, and yields at least two different products depending on the relative concentration of NADH. At [NADH] < K m (40 μM), i.e. [NADH]/[2‐aminobenzoyl‐CoA] ∼ 0.02–0.05, the main product is probably a hydroxylated derivative of 2‐aminobenzoyl‐CoA, which is characterized by an absorbance maximum around 375 nm. When [NADH]/[2‐aminobenzoyl‐CoA] ∼ 2–5, the predominant product is a non‐aromatic coenzyme A thioester (λ max ∼ 320 nm). The stoichiometry in this case is 2.1–2.4 mol NADH oxidized (mol oxygen consumed) −1 (mol 2‐aminobenzoyl‐CoA metabolized) −1 . The product is extremely unstable in the acidic pH range and undergoes decarboxylation in a few minutes at pH < 5. Some degree of stabilisation is obtained upon reduction with sodium borohydride, probably resulting in a further reduced non‐aromatic coenzyme‐A thioester.