EC 5 Isomerases

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Recommended name: 2-aminohexano-6-lactam racemase

Reaction: L-2-aminohexano-6-lactam = D-2-aminohexano-6-lactam

Other name(s): α-amino-ε-caprolactam racemase

Systematic name: 2-aminohexano-6-lactam racemase

Comments: contains pyridoxal 5'-phosphate. Also racemises 2-aminopentano-5-lactam (α-amino-δ-valerolactam) and 2-amino-4-thiahexano-6-lactam (where S replaces CH2 of C-4). It does not catalyse the racemisation of α-amino acids but has some transaminase activity with them.


1. Ahmed, S.A., Esaki, N., Tanaka, H., Soda, K. L-α-Amino-β-thio-ε-caprolactam, a new sulfur-containing substrate for α-amino-&esilon;-caprolactam racemase. FEBS Lett. 174 (1984) 76-79.

2. Ahmed, S.A., Esaki, N., Tanaka, H., Soda, K. Mechanism of α-amino-ε-caprolactam racemase reaction. Biochemistry 25 (1986) 385-388. [PMID: 3955003]


Recommended name: protein-serine epimerase

Reaction: [protein]-L-serine = [protein]-D-serine

Other name(s): protein-serine racemase

Systematic name: [protein]-serine epimerase

Comments: the enzyme specifically interconverts the configuration of Ser-46 of the peptide ω-agatoxin-KT, found in the venom of the funnel web spider, Agelenopsis aperta, but not that of the other serine residue, Ser-28.


1. Shikata, Y., Watanabe, T., Teramoto, T., Inoue, A., Kawakami, Y., Nishizawa, Y., Katayama, K., Kuwada, M. Isolation and characterization of a peptide isomerase from funnel web spider venom. J. Biol. Chem. 270 (1995) 16719-16723. [PMID: 7622482]


Recommended name: ADPglyceromanno-heptose 6-epimerase

Reaction: ADP-D-glycero-D-manno-heptose = ADP-L-glycero-D-manno-heptose

Other name(s): ADP-L-glycero-D-manno-heptose 6-epimerase

Systematic name: ADP-L-glycero-D-manno-heptose 6-epimerase

Comments: requires NAD.


1. Ding, L., Seto, B.L., Ahmed, S.A., Coleman, W.G., Jr. Purification and properties of the Escherichia coli K-12 NAD-dependent nucleotide diphosphosugar epimerase, ADP-L-glycero-D-manno-heptose 6-epimerase. J. Biol. Chem. 269 (1994) 24384-24390. [PMID: 7929099]

2. Raetz, C.R.H. Biochemistry of endotoxins. Annu. Rev. Biochem. 58 (1990) 129-170. [PMID: 1695830]


Recommended name: α-methylacyl-CoA racemase

Reaction: (2S)-2-methylacyl-CoA = (2R)-2-methylacyl-CoA

Systematic name: 2-methylacyl-CoA 2-epimerase

Comments: α-methyl-branched acyl-CoA derivatives with chain lengths of more than C10 are substrates. Also active towards some aromatic compounds (e.g. ibuprofen) and bile acid intermediates, such as trihydroxycoprostanoyl-CoA. Not active towards free acids


1. Schmitz, W., Fingerhut, R., Conzelmann, E. Purification and properties of an α-methylacyl-CoA racemase from rat liver. Eur. J. Biochem. 222 (1994) 313-323. [PMID: 8020470]


Recommended name: L-fucose isomerase

Reaction: L-fucose = L-fuculose

Systematic name: L-fucose ketol-isomerase


1. Lu, Z., Lin, E.C.C. The nucleotide sequence of Escherichia coli genes for L-fucose dissimilation. Nucleic Acids Res. 17 (1989) 4883-4884. [PMID: 2664711]


Recommended name: galactose-6-phosphate isomerase

Reaction: D-galactose 6-phosphate = D-tagatose 6-phosphate

Systematic name: D-galactose-6-phosphate ketol-isomerase

Comments: involved in the tagatose 6-phosphate pathway of lactose catabolism in bacteria.


1. De Vos, W.M., Boerrigter, I., Van Rooijen, R.J., Reiche, B., Hengstenberg, W. Characterization of the lactose-specific enzymes of the phosphotransferase system in Lactococcus lactis. J. Biol. Chem. 265 (1990) 22554-22560. [PMID: 2125052]

2. Van Rooijen, R.J., Van Schalkwijk, S., De Vos, W.M. Molecular cloning, characterization, and nucleotide sequence of the tagatose 6-phosphate pathway gene cluster of the lactose operon of Lactococcus lactis. J. Biol. Chem. 266 (1991) 7176-7181. [PMID: 1901863]


Recommended name: precorrin-8X methylmutase

Reaction: precorrin-8X = hydrogenobyrinate

Other name(s): precorrin isomerase; hydrogenobyrinic acid-binding protein

Systematic name: precorrin-8X 11,12-methylmutase


1. Thibaut, D., Couder, M., Famechon, A., Debussche, L., Cameron, B., Crouzet, J., Blanche, F. The final step in the biosynthesis of hydrogenobyrinic acid is catalyzed by the cobH gene product with precorrin-8X as the substrate. J. Bacteriol. 174 (1992) 1043-1049. [PMID: 1732194]

2. Roth, J.R., Lawrence, J.G., Rubenfield, M., Kieffer-Higgins, S., Church, G.M. Characterization of the cobalamin (vitamin B12) biosynthetic genes of Salmonella typhimurium. J. Bacteriol. 175 (1993) 3303-3316. [PMID: 8501034]

3. Roessner, C.A., Warren, M.J., Santander, P.J., Atshaves, B.P., Ozaki, S., Stolowich, N.J., Iida, K., Scott, A.I. Expression of Salmonella typhimurium enzymes for cobinamide synthesis. Identification of the 11-methyl and 20-methyl transferases of corrin biosynthesis. FEBS Lett. 301 (1992) 73-78. [PMID: 1451790]

4. Crouzet, J., Cameron, B., Cauchois, L., Rigault, S., Rouyez, M.C., Blanche, F., Thibaut, D., Debussche, L. Genetic and sequence analysis of an 8.7-kilobase Pseudomonas denitrificans fragment carrying eight genes involved in transformation of precorrin-2 to cobyrinic acid. J. Bacteriol. 172 (1990) 5980-5990. [PMID: 2211521]


Recommended name: (1[arrow to right]4)-α-D-glucan 1-α-D-glucosylmutase

Reaction: 4-{(1[arrow to right]4)-α-D-glucosyl}n-1-D-glucose = 1-α-D-{(1[arrow to right]4)-α-D-glucosyl}n-1-α-D-glucopyranoside

Other name(s): malto-oligosyltrehalose synthase; maltodextrin α-D-glucosyltransferase

Systematic name: (1[arrow to right]4)-α-D-glucan 1-α-D-glucosylmutase

Comments: the enzyme from Arthrobacter sp., Sulfolobus acidocaldarius acts on (1[arrow to right]4)-α-D-glucans containing three or more (1[arrow to right]4)-α-linked D-glucose units. Not active towards maltose.


1. Maruta, K., Nakada, T., Kubota, M., Chaen, H., Sugimoto, T., Kurimoto, M., Tsujisaka, Y. Formation of trehalose from maltooligosaccharides by a novel enzymatic system. Biosci. Biotechnol. Biochem. 59 (1995) 1829-1834. [PMID: 8534970]

2. Nakada, T., Maruta, K., Tsusaki, K., Kubota, M., Chaen, H., Sugimoto, T., Kurimoto, M., Tsujisaka, Y. Purification and properties of a novel enzyme, maltooligosyl trehalose synthase, from Arthrobacter sp. Q36. Biosci. Biotechnol. Biochem. 59 (1995) 2210-2214. [PMID: 8611744]

3. Nakada, T., Ikegami, S., Chaen, H., Kubota, M., Fukuda, S., Sugimoto, T., Kurimoto, M., Tsujisaka, Y. Purification and characterization of thermostable maltooligosyl trehalose synthase from the thermoacidophilic archaebacterium Sulfolobus acidocaldarius. Biosci. Biotechnol. Biochem. 60 (1996) 263-266. [PMID: 9063973]


Recommended name: maltose α-D-glucosyltransferase

Reaction: maltose = α,α-trehalose

Other name(s): trehalose synthase; maltose glucosylmutase

Systematic name: maltose α-D-glucosylmutase


1. Nishimoto, T., Nakano, M., Ikegami, S., Chaen, H., Fukuda, S., Sugimoto, T., Kurimoto, M., Tsujisaka, Y. Existence of a novel enzyme converting maltose to trehalose. Biosci. Biotechnol. Biochem. 59 (1995) 2189-2190.

2. Nishimoto, T., Nakano, M., Nakada, T., Chaen, H., Fukuda, S., Sugimoto, T., Kurimoto, M., Tsujisaka, Y. Purification and properties of a novel enzyme, trehalose synthase, from Pimelobacter sp. R48. Biosci. Biotechnol. Biochem. 60 (1996) 640-644. [PMID: 8829531]



Recommended name: dopachrome isomerase

Reaction: L-dopachrome = 5,6-dihydroxyindole-2-carboxylate

Other name(s): dopachrome tautomerase; tyrosinase-related protein 2 (TRP2); dopachrome δ72-isomerase; dopachrome δ-isomerase

Systematic name: dopachrome keto-enol isomerase

Comments: a zinc enzyme. Stereospecific for L-dopachrome (5,6-dioxo-2,3,5,6-tetrahydroindole-2-carboxylate). Dopachrome methyl ester is a substrate, but dopaminochrome (2,3-dihydroindole-5,6-quinone) is not.


1. Solano, F., Jiménez-Cervantes, C., Martinez-Liarte, J.H., Garcia-Borrón, J.C., Lozano, J.A. Molecular mechanism for catalysis by a new zinc enzyme, dopachrome tautomerase. Biochem. J. 313 (1996) 447-453. [PMID: 8573077]

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