EC 5 Isomerases

EC 5.1.1.15

Recommended name: 2-aminohexano-6-lactam racemase

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

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

Systematic name: 2-aminohexano-6-lactam racemase

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

References:

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

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

EC 5.1.1.16

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 Ser⁴⁶ of the peptide -agatoxin-KT, found in the venom of the funnel web spider, Agelenopsis aperta, but not that of the other serine residue, Ser²⁸

References:

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]

EC 5.1.3.20

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.

References:

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]

EC 5.1.99.4

Recommended name: -methylacyl-CoA racemase

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

Systematic name: 2-methylacyl-CoA 2-epimerase

Comments: -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

References:

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

EC 5.3.1.25

Recommended name: L-fucose isomerase

Reaction: L-fucose = L-fuculose

Systematic name: L-fucose ketol-isomerase

References:

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]

EC 5.3.1.26

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.

References:

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]

EC 5.4.1.2

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

References:

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]

EC 5.4.99.15

Recommended name: (14)--D-glucan 1--D-glucosylmutase

Reaction: 4-{(14)--D-glucosyl}_n-1-D-glucose = 1--D-{(14)--D-glucosyl}_n-1--D-glucopyranoside

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

Systematic name: (14)--D-glucan 1--D-glucosylmutase

Comments: the enzyme from Arthrobacter sp., Sulfolobus acidocaldarius acts on (14)--D-glucans containing three or more (14)--linked D-glucose units. Not active towards maltose.

References:

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]

EC 5.4.99.16

Recommended name: maltose -D-glucosyltransferase

Reaction: maltose = ,-trehalose

Other name(s): trehalose synthase; maltose glucosylmutase

Systematic name: maltose -D-glucosylmutase

References:

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]

AMENDMENTS TO EXISTING ENTRIES

EC 5.3.3.12

Recommended name: dopachrome isomerase

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

Other name(s): dopachrome tautomerase; tyrosinase-related protein 2 (TRP2); dopachrome ⁷,²-isomerase; dopachrome -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.

References:

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, dopachrometautomerase. Biochem. J. 313 (1996) 447-453. [PMID: 8573077]