Reaction: (S)-mandelate + acceptor = phenylglyoxylate + reduced acceptor
For diagram click here.
Glossary: (S)-mandelate = (S)-2-hydroxy-2-phenylacetate
phenylglyoxylate = benzoylformate = 2-oxo-2-phenylacetate
Other name(s): MDH (ambiguous)
Systematic name: (S)-2-hydroxy-2-phenylacetate:acceptor 2-oxidoreductase
Comments: This enzyme is a member of the FMN-dependent α-hydroxy-acid oxidase/dehydrogenase family [1]. While all enzymes of this family oxidize the (S)-enantiomer of an α-hydroxy acid to an α-oxo acid, the ultimate oxidant (oxygen, intramolecular heme or some other acceptor) depends on the particular enzyme. This enzyme transfers the electron pair from FMNH2 to a component of the electron transport chain, most probably ubiquinone [1,2]. It is part of a metabolic pathway in Pseudomonads that allows these organisms to utilize mandelic acid, derivatized from the common soil metabolite amygdalin, as the sole source of carbon and energy [2]. The enzyme has a large active-site pocket and preferentially binds substrates with longer sidechains, e.g. 2-hydroxyoctanoate rather than 2-hydroxybutyrate [1]. It also prefers substrates that, like (S)-mandelate, have β unsaturation, e.g. (indol-3-yl)glycolate compared with (indol-3-yl)lactate [1]. Esters of mandelate, such as methyl (S)-mandelate, are also substrates [3].
Links to other databases: BRENDA, EXPASY, KEGG, PDB, CAS registry number: 9067-95-2
References:
1. Lehoux, I.E. and Mitra, B. (S)-Mandelate dehydrogenase from Pseudomonas putida: mechanistic studies with alternate substrates and pH and kinetic isotope effects. Biochemistry 38 (1999) 5836-5848. [PMID: 10231535]
2. Dewanti, A.R., Xu, Y. and Mitra, B. Role of glycine 81 in (S)-mandelate dehydrogenase from Pseudomonas putida in substrate specificity and oxidase activity. Biochemistry 43 (2004) 10692-10700. [PMID: 15311930]
3. Dewanti, A.R., Xu, Y. and Mitra, B. Esters of mandelic acid as substrates for (S)-mandelate dehydrogenase from Pseudomonas putida: implications for the reaction mechanism. Biochemistry 43 (2004) 1883-1890. [PMID: 14967029]