Anaerobic degradation of 2-aminobenzoic acid (anthranilic acid) via benzoyl-coenzyme A (CoA) and cyclohex-1-enecarboxyl-CoA in a denitrifying bacterium.
The enzymes catalyzing the initial reactions in the anaerobic degradation of 2-aminobenzoic acid (anthranilic acid) were studied with a denitrifying Pseudomonas sp. anaerobically grown with 2-aminobenzoate and nitrate as the sole carbon and energy sources. Cells grown on 2-aminobenzoate are simultaneously adapted to growth with benzoate, whereas cells grown on benzoate degrade 2-aminobenzoate several times less efficiently than benzoate. Evidence for a new reductive pathway of aromatic metabolism and for four enzymes catalyzing the initial steps is presented. The organism contains 2-aminobenzoate-coenzyme A ligase (2-aminobenzoate-CoA ligase), which forms 2-aminobenzoyl-CoA. 2-Aminobenzoyl-CoA is then reductively deaminated to benzoyl-CoA by an oxygen-sensitive enzyme, 2-aminobenzoyl-CoA reductase (deaminating), which requires a low potential reductant [Ti(III)]. The specific activity is 15 nmol of 2-aminobenzoyl-CoA reduced min-1 mg-1 of protein at an optimal pH of 7. The two enzymes are induced by the substrate under anaerobic conditions only. Benzoyl-CoA is further converted in vitro by reduction with Ti(III) to six products; the same products are formed when benzoyl-CoA or 2-aminobenzoyl-CoA is incubated under reducing conditions. Two of them were identified preliminarily. One product is cyclohex-1-enecarboxyl-CoA, the other is trans-2-hydroxycyclohexane-carboxyl-CoA. The complex transformation of benzoyl-CoA is ascribed to at least two enzymes, benzoyl-CoA reductase (aromatic ring reducing) and cyclohex-1-enecarboxyl-CoA hydratase. The reduction of benzoyl-CoA to alicyclic compounds is catalyzed by extracts from cells grown anaerobically on either 2-aminobenzoate or benzoate at almost the same rate (10 to 15 nmol min-1 mg-1 of protein). In contrast, extracts from cells grown anaerobically on acetate or grown aerobically on benzoate or 2-aminobenzoate are inactive. This suggests a sequential induction of the enzymes.
Lochmeyer
C
C
Angewandte Mikrobiologie, University of Ulm, Germany.
Koch
J
J
Fuchs
G
G
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000220:Adaptation, Biological; D000693:Anaerobiosis; D001565:Benzoates / Q000378:metabolism; D019817:Benzoic Acid; D003066:Coenzyme A Ligases / Q000378:metabolism*; D004790:Enzyme Induction; D004798:Enzymes / Q000032:analysis; D009566:Nitrates / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism; D011549:Pseudomonas / Q000378:metabolism*; D062367:ortho-Aminobenzoates / Q000378:metabolism*
D000214:Acyl Coenzyme A; D001565:Benzoates; D004798:Enzymes; D009566:Nitrates; D009573:Nitrites; C074781:cyclohex-1-enecarboxyl-coenzyme A; D062367:ortho-Aminobenzoates; C031385:anthranilic acid; C037817:benzoyl-coenzyme A; D019817:Benzoic Acid; C074780:2-aminobenzoyl-CoA reductase (deaminating); D000587:Oxidoreductases Acting on CH-NH Group Donors; C070685:2-aminobenzoate coenzyme A ligase; D003066:Coenzyme A Ligases