Ring cleavage enzyme

Buchan A, LS Collier, EL Neidle, MA Moran (2000) Key aromatic-ring-cleavage enzyme, protocatechuate 3,4-dioxygenase, in the ecologically important marine Roseobacter lineage. Appl Environ Microbiol 66 4662-4672. 

Lendenmann U, JC Spain (1996) 2-aminophenol 1,6-dioxygenase a novel aromatic ring cleavage enzyme purified from Pseudomonas pseudoalcaligenes JS 45. J Bacteriol 178 6227-6232. 

Gescher J, W Eisenreich, J Wort, A Bacher, G Fuchs (2005) Aerobic benzoyl-CoA catabolic pathway inAzoarcus evansii studies on the non-oxygenolytic ring cleavage enzyme. Mol Microbiol 56 1586-1600. 

Pelletier DA, CS Harwood (1998) 2-ketohexanecarboxyl coenzyme A hydrolase, the ring cleavage enzyme required for anaerobic benzoate degradation by Rhodopseudomonas palustris. J Bacteriol 180 2330-2336. 

The ring-cleavage enzymes are of two broad classes, and only some illustrative examples are given. 

Earlier we indicated that an alternative strategy to prevent ring cleavage is to use selective inhibition of the enzymes which catabolise the ring structure. 

Most enzymes that catalyze the cleavage of heterocyclic compounds are scantily understood and most of them have not even been identified. Different types of enzymes are involved in various heterocyclic ring cleavage reactions (see schemes in Fig. 33). 

Lignin peroxidase of Phanerochaete chrysosporium catalyzes the ring cleavage of /3-0-4 lignin substructure model compounds and synthetic lignin (DHP). A mechanism for the ring cleavage by the enzyme is described. 

The purpose of the present paper is to describe the aromatic ring cleavage of lignin substructure model compounds by white-rot basidiomycetes and by lignin peroxidase of P. chrysosporium. The aromatic ring cleavage of synthetic lignin (DHP) by the enzyme will also be described. 

The muconate of arylglycerol 12-Et retains all six carbon atoms of the B-ring of the substrate 1-Et. Hence, this product seemed to be appropriate to examine mechanisms for the ring cleavage. Based on the results of tracer experiments, we proposed a ring cleavage mechanism for the enzyme (7,9), as now described. Degradation of l,3-dihydroxyl-l-(4-ethoxy-... 

Similar mechanisms were also proposed for the ring cleavage of veratryl alcohol (22,23) and a 0-0-4 lignin substructure model (24) by the enzyme. 

---