ExplorEnz: EC 4.2.1.175

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4.2.1.175

Accepted name:

(R)-3-(aryl)lactoyl-CoA dehydratase

Reaction:

(1) (R)-3-(phenyl)lactoyl-CoA = (E)-cinnamoyl-CoA + H₂O
(2) (R)-3-(4-hydroxyphenyl)lactoyl-CoA = (E)-4-coumaroyl-CoA + H₂O
(3) (R)-3-(indol-3-yl)lactoyl-CoA = 3-(indol-3-yl)acryloyl-CoA + H₂O

Other name(s):

fldBC (gene names); (R)-phenyllactoyl-CoA dehydratase; aryllactyl-CoA dehydratase

Systematic name:

(R)-3-(aryl)lactoyl-CoA hydro-lyase

Comments:

The enzyme, found in some amino acid-fermenting anaerobic bacteria, participates in the fermentation pathways of L-phenylalanine, L-tyrosine, and L-tryptophan. It is a heterodimeric protein consisting of the FldB and FldC polypeptides, both of which contain an [4Fe-4S] cluster, and forms a complex with EC 2.8.3.17, 3-(aryl)acryloyl-CoA:(R)-3-(aryl)lactate CoA-transferase (FldA). In order to catalyse the reaction, the enzyme requires one high-energy electron that transiently reduces the electrophilic thiol ester carbonyl of the substrate to a nucleophilic ketyl radical anion, facilitating the elimination of the hydroxyl group. This electron, which is provided by by EC 5.6.1.9, (R)-2-hydroxyacyl-CoA dehydratase activating ATPase, needs to be supplied only once, before the first reaction takes place, as it is regenerated at the end of each reaction cycle. The enzyme acts on (R)-3-(aryl)lactoyl-CoAs produced by FldA, and regenerates the CoA donors used by that enzyme.

Links to other databases:

BRENDA, EXPASY, KEGG, MetaCyc

References:

1.	Dickert, S., Pierik, A.J., Linder, D. and Buckel, W. The involvement of coenzyme A esters in the dehydration of (R)-phenyllactate to (E)-cinnamate by Clostridium sporogenes. Eur. J. Biochem. 267 (2000) 3874–3884. [DOI] [PMID: 10849007]
2.	Dickert, S., Pierik, A.J. and Buckel, W. Molecular characterization of phenyllactate dehydratase and its initiator from Clostridium sporogenes. Mol. Microbiol. 44 (2002) 49–60. [PMID: 11967068]
3.	Kim, J., Hetzel, M., Boiangiu, C.D. and Buckel, W. Dehydration of (R)-2-hydroxyacyl-CoA to enoyl-CoA in the fermentation of α-amino acids by anaerobic bacteria. FEMS Microbiol. Rev. 28 (2004) 455–468. [PMID: 15374661]
4.	Kim, J., Darley, D.J., Buckel, W. and Pierik, A.J. An allylic ketyl radical intermediate in clostridial amino-acid fermentation. Nature 452 (2008) 239–242. [PMID: 18337824]
5.	Dodd, D., Spitzer, M.H., Van Treuren, W., Merrill, B.D., Hryckowian, A.J., Higginbottom, S.K., Le, A., Cowan, T.M., Nolan, G.P., Fischbach, M.A. and Sonnenburg, J.L. A gut bacterial pathway metabolizes aromatic amino acids into nine circulating metabolites. Nature 551 (2017) 648–652. [PMID: 29168502]

[EC 4.2.1.175 created 2019]